01 Evolution 1-4

L.H. Schmitt 1 2014

The University of Western Australia School of Anatomy, Physiology and Human Biology

Human Biology I Dr Linc Schmitt

Evolution and Human Biology Lectures: 1. First principles of evolution

2. Charles Darwin 3. Evidence for evolution and natural selection 4. Evolution and life on Earth

Reading: Futuyma DJ (2005) Evolution. Sinauer Associates, Sunderland Price PW (1996) Biological evolution. Saunders, Orlando Relethford J (2013) The human species: an introduction to biological anthropology (9th ed). Introduction and chapters 1, 4 and 8 Ridley M (1997) Evolution. Oxford University Press, Oxford Hall BK & Hallgrimsson B (2008) Strickbergers Evolution. Jones and Bartlett, Sudbury, Massachusetts Check out the Science Library. Browse the shelves around call numbers 575 and 576.

Evolution and Human Biology 1: First principles of evolution Pre-reading: Saladin KS (2012) Anatomy and physiology: the unity of form and function (6th ed) pp7-10.

Perspective Human Biology is concerned with

What the human body is and how it works- its structure, function, development and growth

Why it is like this evolution, variation and ecology

Who we are biosocial interactions (ie the interplay between biology and culture)

The Nobel Prize winner Sir Peter Medewar wrote that For a biologist the alternative to thinking in evolutionary terms is not to think at all. Human Biology I begins by introducing the concept of evolution because this is the unifying framework within which the biology of humans, and indeed all life on Earth, is understood.

In Human Biology, the term evolution usually means biological evolution or organic evolution. Evolution can be defined as biological change over time, though more strictly speaking it is genetic change in a population over generations.

Evolution is present in our everyday life. There are excellent examples, both recent and on-going. For example, virtually all the pets we keep and the foods we eat have undergone substantial evolutionary change in recent times. These are examples of humans intentionally directing the evolution of other species, a phenomenon known as domestication or artificial selection. The process can occur because (1) within a species, not all individuals are exactly the same - ie there is inherited variation; and (2) if some forms (types or variants) have more offspring than others, the frequency of the variants can change - ie natural selection occurs.

Humans have also influenced the evolution of other species through unintentional alterations of the environment. For example, in Europe during the 19th Century, industrialization led to pollution which forced changes in other species (eg melanism in moths). Similarly, our use of antibiotics has increased the frequency of micro-organisms such as bacteria that are resistant to these antibiotics (through selection for

resistant forms); and the use of insecticides has increased the frequency of insects that are resistant to these insecticides. These changes have had major impacts upon our lifestyle. When first used, antibiotics and insecticides are usually very effective. However, after prolonged use some diseases transmitted by insects, such as malaria, have become more common again because of the reduced effectiveness of insecticides. And new forms of micro-organisms that are resistant to antibiotics have evolved and these can sometimes be lethal.

When asked to give examples of evolution, most newcomers to biology turn to examples from the fossil record, such as changes in the cranium of hominids (humans and their recent ancestors), which illustrate the long-term nature of evolution. Indeed, evolution has been in progress on this planet for at least 3.5 billion years.

Evolution requires the existence of inherited variation in a population. This is ubiquitous all populations of all species have variation that is genetically determined (ie inherited). If some inherited variants confer greater reproductive success than others then evolution by natural selection will occur.

Evolution is a biological law, in much the same way that we have discovered physical laws such as the laws of motion and gravity. These laws have enormous explanatory power that make them amenable to study (and falsification). One of the major things science has discovered is that all the different forms of life on Earth come from a single common ancestor that existed more than 3.5 billion years ago. This is not a necessary consequence of evolution, but neither is it surprising, when we understand how evolution works.

Evolution is the core theme running through all biological disciplines. The Russian-born American biologist Theodosius Dobzhansky wrote that Nothing in biology makes sense except in the light of evolution. This highlights the importance of evolution for understanding our own biology.

Human Biology

2014 Human Biology I

L.H. Schmitt 2 Evolution and Human Biology

`

Outline Preamble: (a) Resources & Rules

(b) What is Human Biology? 1. What is evolution? 2. Some examples of evolution 3. Variation 4. Natural selection 5. Consequences of evolution

Terms Common ancestry Domestication (Artificial selection) Evolution Fitness Natural selection Variation

Like all sciences, Human Biology takes a reductionist approach to understanding how things work ie by studying the parts that make up the whole. However, simultaneously, human biology takes a strong holistic approach by being concerned with the whole, not just the parts. This is based upon the supposition that humans are complex and will have emergent properties ie some things cannot be predicted (or at least not easily so) just from an understanding of the components alone.

[from: Gary Larson The Far Side]

The basic concept of Natural Selection is very simple (once understood!) but can be quite difficult to grasp at first. If there is inherited variation in a population (this is inevitable given the principles of genetics) and some variants (genes) confer on the individual greater average reproductive success than other variants, then the frequency of the variants will change. This is evolution by natural selection. The measure of reproductive success is termed fitness (specifically Darwinian fitness or evolutionary fitness) dont confuse this term with somatic fitness (e.g. how fast you can run or your health status etc).

When coining the term, Darwin wrote in The Origin of Species This preservation of favourable variations and the rejection of injurious variations, I call Natural Selection. (C Darwin, 1859, On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. p81).


Domestication by artificial selection. Top - Colour variation in budgies. Budgerigars are the worlds smallest parrot and native to arid Australia. In the wild, individuals are typically green with a yellow head. For a small proportion of individuals in a population near Derby in WA, the yellow colour is more widespread on the body. This illustrates that variation in colour exists in natural populations. This species has been domesticated in recent times - after Europeans came to Australia. This has involved choosing (ie selecting) rare variants for breeding purposes. These variants involve feather colour, pattern and shape as well as size some domesticated budgies are 3 times larger than the wild form - and have led to an enormous variety of domestic forms. You can see these pictures in colour on the web.

Bottom In the 16th century wheat plants were about 1.5 metres high (top section) but now there are many dwarf varieties of wheat (lower section). Artificial selection was used to lessen the height. Dwarf varieties have advantages; they put less effort into growing the stem and more into producing seed, and they are less susceptible to wind damage.

Darwin used domesticated species to illustrate the principles of natural selection namely that individuals are not all the same (variation exists) and that if some variants have greater reproductive success than others, and the variation is inherited, the frequencies will change. Virtually all the food we now eat (plant and animal) and our pets have been modified, and continue to be modified, through domestication.

[from: Top - Campbell (1996) Biology. (4th ed) Benjamin Cummings, California. p246. Bottom Watson (2003) DNA: the secret of life. Heinemann, London. p157]

Human Biology I 2014

Evolution and Human Biology 3 L.H. Schmitt

Industrial melanism in the peppered moth, Biston betularia illustrating evolution in action. Each photograph includes two moths one that is black (known as the melanic form) and another that is light coloured with black speckling (known as the typical form).

In England, prior to the Industrial Revolution in the middle of the 19th Century, virtually all individuals were the lighter, typical form. This can be seen from collectors records and museum specimens (moth collecting has been a very popular hobby in Britain!) but it is also clear that melanic individuals occurred occasionally at this time.

During the Industrial Revolution, and up until the middle of the 20th Century, the melanic form was the most common in many parts of Britain. The black shading in the pie diagrams on the map records the proportion of melanic forms at various places around 1950. The frequencies of the two forms of peppered moths depended on the extent of pollution. The melanic forms were at their highest frequencies downwind from industrial regions (where pollution was greatest) and lowest where pollution was low or absent (eg Welsh and Scottish highlands).

As shown in the graph, in the last 50 years the typical form has once again become the common form with the melanic forms decline in frequency. These changes are associated with declining levels of pollution. For about 100 years, starting with the Industrial Revolution, the trunks of trees were blackened by soot but, with anti-pollution laws enacted from about 1960, the tree trunks have returned to their natural state.

The exact reason for the changes in frequencies of the moth forms is not known. An earlier explanation, based a differential predation, has been seriously challenged (i.e the explanation implied by the Larson cartoon may be incorrect). Nonetheless, the evidence that the change did occur and that pollution was a key factor remains strong.

There are over 200 different species of moths and related organisms in Europe and North America that show similar changes in colour associated with changes in pollution.

The difference between the two colour forms is inherited and these observations show that the frequency of genetic variants can change over time.

[from: Top - Ayala & Valentine (1979) Evolving: the theory and processes of organic evolution. Benjamin Cummings, California. p133. Second - Frankham et al (2002) Introduction to conservation genetics. Cambridge University Press, Cambridge, p138. Third - Futuyma (2005) Evolution. Sinauer, Sunderland Massachusetts, p293. Bottom Gary Larson The Far Side]



Bacteria often evolve resistance to antibiotics. An increase in antibiotic resistance can be linked to the increased use of the antibiotic. The graph shows the rise in the use of an antibiotic in a community in Finland. With the increased use of the drug, to treat middle-ear infection in children, came a parallel increase in the proportion of the bacteria with drug resistance.

[from: Futuyma (2005) Evolution. Sinauer, Sunderland Massachusetts, p3]

Some people who are exposed to the HIV virus remain uninfected and others, while infected, survive much longer than expected. This resistance to HIV infection and AIDS is associated with the CCR5-32 gene. This gene is quite frequent in northern Europeans (~10%) but virtually absent from Africa and Asia. HIV infection is less common in Europe and more common where the CCR5-32 gene is absent. There are other genes conferring susceptibility or resistance to HIV.

It is not known why the CCR5-32 gene is in such high frequency in Europe - it is not due to natural selection for resistance to HIV because the high frequency of the gene predates the arrival of HIV in Europe. One hypothesis is that it confers resistance to another infective agent that was common in the past (e.g. bubonic plague) and during this previous time it therefore had a selective advantage and increased in frequency. However, there are other explanations (e.g. genetic drift which is discussed in Human Biology II).

While the CCR5-32 gene seems to confer a level of resistance to HIV infection it increases susceptibility to other infections (e.g. West Nile virus) a good illustration of no free lunches in evolution! This perhaps also explains why the gene is in low frequency in other parts of the world.

[from: Freeman & Herron (2004) Evolutionary analysis. (3rd ed) Pearson, Upper Saddle River, New Jersey. Figure 1-11]

Changes in the fossil record illustrate evolution. Comparison of a modern human skull (bottom) with two fossil species, Homo erectus (top) and H sapiens neanderthalensis (middle). This is one example showing a change over time in the fossil record. It was evidence of this type the existence of forms that are not seen today (ie are extinct) - that led some biologists to believe that the forms of life were not constant but changed over time. In many cases (probably most) the fossil forms are not on a path to modern forms but represent extinct lineages. However, some represent lineages that are still present today.

The drawing at the bottom shows some of the changes during the evolution of horses (from left to right). The numbers on the first row indicate size changes. The second row illustrates changes in the limbs, including toes. There were also changes in the skull, and in particular the teeth, as the diet changed. It appears that changes in the environment were key drivers of this evolution. While these morphological changes appear to be quite simple and an example of straight-line evolution, evolution of the horse was far more complex than shown here.

[from: Top - Lewin (1989) Human evolution: an illustrated introduction. (2nd ed) Blackwell, Boston. p103. Bottom Villee et al (1968) General zoology. P 660]



Time

About 500 million years BP (before present)

Natural selection is a process i.e. it is a name given to something that happens. Evolution by natural selection is analogous to a trial and error process just as if we bought many lottery tickets (trials) most will be worthless (errors) but one may win, so there are lots a genetic variants produced (mutations are analogous to trials) with most having lower fitness than the original (errors) but one may prove to be beneficial and replace the previous common variant. Natural selection is a biological law and, like the laws in the physical sciences, has enormous explanatory powers. For example it explains the adaptations of species to their environment something we return to later in this unit and in Human Biology II.


Vertebrate phylogeny (evolutionary history). All vertebrates (animals with backbones) evolved from a common ancestor that lived about 500 million years ago. The diagram shows the main branches since that time. This diagram has an unmarked time axis, starting at the bottom, 500 MY before present, and extending up to the top which is at the present day.

Darwins theory of evolution predicted that not only would forms of life change over generations in a lineage (anagenesis) but also that lineages would split (cladogenesis). Each bifurcation (split) in the

diagram represents a major cladogenetic event.

There are many others branches in this tree that are not shown here for reasons of simplicity. All the species that exist today will have their own branch. In addition, there will be many branches that did not reach the present; ie lineages that became extinct. There were probably hundreds of thousands, if not millions of branches in the vertebrate tree.

It is not only vertebrates that can be shown to be linked together in a single evolutionary divergence - all forms of life on the planet have some peculiar but identical features in common, an indication that we all share a common ancestry and belong to the same evolutionary tree. This is not an inevitable outcome of Darwins theory, but it is also not unexpected, and is a key piece of evidence that helps substantiate the theory.

[from: Ridley (1993) Evolution. Blackwell, Boston. p368]

There are examples of evolution all around us indeed all of life on Earth (at least all life that has so far been studied) is the result of one large evolutionary divergence. Evolution requires a system of reproduction, inherited variation, and differential reproductive success (fitness differences). A key factor driving evolution is the environment, which is continually changing. As a result, species must, more or less, continuously adapt (ie evolve) to be successful (ie reproduce) in the new conditions. This is a little like the Red Queen in Alice Through The Looking Glass (Lewis Carroll). The Red Queen had to run to stay in the same place rather like being on a treadmill. In an analogous way, species need to change (ie evolve) to remain viable because the environment in which they exists is continually changing. If they dont evolve individuals are likely to have reduced fitness and the species is then vulnerable to extinction.




Evolution and Human Biology 2: Charles Darwin Pre-reading: Relethford (9th ed) pp11-14 and pp25-30

Perspective The great French geneticist Francois Jacob, who won the Nobel Prize for discovering mechanisms by which gene activity is regulated, wrote in 1973 that there are many generalizations in biology, but precious few theories. Among these, the theory of evolution is by far the most important, because it draws together from the most varied sources a mass of observations which would otherwise remain isolated; it unites all the disciplines once concerned with living beings; it establishes order among the extraordinary variety of organisms and closely binds them to the rest of the earth; in short, it provides a causal explanation of the living world and its heterogeneity. (F Jacob, 1973, The Logic of Life. Princeton University Press, Princeton. p 13) Prior to Darwin, the European view of the living world was dominated by the Great Chain of Being. This concept had its origins in ancient Greece and considered all life (and aspects of the non-living world) to be part of a hierarchical sequence from the most simple to the most complex. At the bottom of this sequence was inanimate matter such as earth and water (and fire), followed, in order, by plants, then animals, then humans, then angels. A key feature of this view was that all the categories were fixed, designed by God, and the task for biologists was to work out this design. This rigid, self-centred view of the world was changed through a series of scientific revolutions instigated by Copernicus and Galileo - who demonstrated that the Earth is not at the centre of the universe; Hutton and Lyle - who showed that the Earth is very old and continually changing by processes still active today (uniformitarianism); and then Darwin - who showed that the biological world is also subject to much change (organic evolution) and most importantly elaborated a mechanism for that change. Both Copernicus and Darwins views were met with stiff resistance from parts of their societies, especially the churches. Religion and science are not in opposition unless one takes a limited and literal interpretation of creation stories. All human groups have belief systems that incorporate explanations for how the world came about; these form part of their religions. Today, most Biblical scholars of those religions based on the Old Testament (Christian, Islamic, Judaism) do not take the descriptions in Genesis as literal explanations, but rather see them as allegories. On the other hand, many evolutionary biologists are deeply religious and see no conflict between their science and religion, with some believing in a theistic evolution biological evolution has been Gods way of making the organic world. What is clear is that for the mainstream churches, and their members, science and religion are not in conflict. They play different roles in societies, with different concerns one

primarily with the spiritual world and the other with the natural world. So, how does Science go about discovering how the world works? A simple view is that scientific understanding is achieved through a hypothetico-deductive process which has four steps. (a) Ideas are generated (creative events) (b) that lead to predictions (hypotheses) (c) that are then tested (via experimentation and observation). As a result of these tests (d) the hypotheses are either rejected (falsification) or not rejected. Hypotheses cannot be proven. If, after many tests a hypothesis is not rejected (and alternative explanations are rejected) then it may come to be considered the best explanation of a phenomenon. Falsification is sometimes referred to as proof by rejection. In science, the term theory is used to describe a group of hypotheses that are accepted and together provide statements of principles or laws that explain major phenomenon ie that paint a big picture.

Because scientific understanding arises by methods that are fundamentally different from how religious beliefs are obtained (ie by received wisdom), it is not possible for science to give credence to Biblical or other religion-based explanations of creation (of which there are hundreds). Charles Darwin had an intense interest in nature. He was recruited as the naturalist for the voyage of the Beagle a five year odyssey, mainly around South America and the Pacific. His major contributions to evolutionary biology were to provide an astounding amount of evidence in favour of evolution occurring and, most importantly, a mechanism for how it could occur (natural selection). He didnt invent evolution it was a phenomenon widely accepted amongst biologists of his time, but mainly in the context of changes within a lineage ie that a species could gradually change over time, a phenomenon called anagenesis. Darwin appreciated that lineages could also diverge that a single species, after being separated into two geographically separate populations, could give rise to two different species. This is the concept of cladogenesis (divergent evolution). Note that cladogenesis also requires anagenesis (changes within a lineage) for the two populations to become different after they have been geographically separated. After writing an outline of his ideas, Darwin then spent over 20 years accumulating evidence. It was only when Alfred Russel Wallace wrote to him, expressing essentially the same idea, that Darwin was persuaded to publish his conclusions primarily through his book The origin of species published in 1859. Its full title is On the origin of species by means of natural selection or the preservation of favoured races in the struggle for life!

Outline 1. Science, evolution, religious beliefs and pre-Darwinian thought

Conflicts between science and religion How science is done Pre-Darwinian thoughts Challenges to rigidity

2. Charles Darwin Darwins life Voyage of the Beagle Outline of his ideas



Terms Anagenesis Cladogenesis Falsification Great Chain of Being

Scale of Nature Hypothetico-deductive process Theory Uniformitarianism

People & Places Aristotle Copernicus Galileo Hutton Lyle Wallace Galapagos Islands Temple of Serapis

Creationism. Title of an article by A. F. Campbell in Eureka Street (1997) Jesuit Publications, Melbourne. May, p30-34. The author is Professor of Old Testament at the Jesuit Theological College within the United Faculty of Theology, Melbourne.

Some quotes from the article:

"As a Bible person, it maddens me to read claims that creationism takes the Bible literally. It does not. There are numerous portrayals of creation in the Bible and there are radical differences between them."

"I do not begrudge scientists their complaint that creationists distort, misunderstand, and misapply science in the presentation of their creationists views. It is the right of scientists to defend their bailiwick."

"What I object to intensely is any claim by creationists or on behalf of creationists that their view emerges from a literal understanding of the Bible. That is my bailiwick and I will defend it. Creationism as a literal understanding of the Bible is bunk."

A representation of Aristotles Scala Naturae (Scale or Ladder of Nature) which led to The Great Chain of Being. This was a European view of the world prevalent up until the 19th Century. All life forms were positioned on the ladder in an order which was believed to represent Gods design. Within categories there were sub-categories so, for example, animals began with jellyfish and the like, followed by invertebrates and then vertebrates. Indeed, all organisms had a position in the Chain and even humans were organized according to their social position ie whether they were slaves, foreigners, royalty etc.

[from: Strickberger (1990) Evolution. Jones and Bartlett, Boston. p6]

Remains of the Temple of Serapis, a Roman temple near Naples. A few metres up from the base, the columns surfaces are roughened because they have been bored by a marine mollusc. This shows that the columns spent time partly submerged under the sea. The temple was built on dry land, which subsequently sunk (or the sea-level rose) and then rose again. Lyle used this as one illustration of Uniformitarianism the continual change in the Earths surface due to erosion (wind and water), volcanic activity, earthquakes, tectonic movements and the like. Darwin realized that these changes would also impact life forms.

[from: Price (1996) Biological evolution. Saunders, Orlando. p29]



Charles Darwin as a young man. Darwin didnt invent evolution many people before him, including his grandfather, realized that evolution must have happened. After dropping out of university twice he went on to become the most influential scientist of the 19th Century! His attention to accumulating detailed evidence, to synthesize and incorporate the work of others into his own ideas, and the ability to write clearly in a style that was easily comprehensible were important factors in his success.

[from: Moorehead (1971) Darwin and the Beagle. Penguin, Melbourne. p23]

Far left - The Beagle in Sydney harbour.

Left - Voyage of the Beagle. Even though we associate the Galapagos islands with Darwins ideas, he spent little time there and didnt appreciate the significance of his collections and observations until after he returned to England. His geological observations in South America were initially of much greater interest to him.

[from: Moorehead (1971) Darwin and the Beagle. Penguin, Melbourne. Frontispiece and pp16-17]

All species show biological variation. Inherited biological variation is the source of evolutionary change. This variation arises by the process of mutation. Humans also exhibit extensive cultural variation for example the clothes we wear, hairstyles, the food we eat, religion and other belief systems, behaviour etc. While cultural variation increases the total variation and is not itself directly subject to evolutionary forces, it can influence biological evolution. How might it do this?

[from: Annals of Human Biology. Taylor & Francis, London. Front cover]

Alfred Russel Wallace wrote to Darwin in 1858, expressing the idea of natural selection. Wallace was a biologist collecting animals in eastern Indonesia. This is the region where two of the worlds most different faunal groups merge - Oriental and Australian - and is now known amongst biologists as Wallacea. While Wallace can justly lay claim to discovering independently the concept of natural selection, Darwin in fact had done so 20 years before, but had not published his ideas. Even before Darwin, others had similar ideas but did not develop them.

[from: Futuyma (1986) Evolutionary biology (2nd ed). Sinauer, Massachusetts. p5]



One speciesOne species

2 species

Two isolated populations

Two isolated populations

TimeTime

Geographicseparation

Geographicseparation

Different environments

Reproductive

isolation

Natural selection+

other evolutionary forces

timetimeAnagenesisCladogenesis

Evolution within a line of descent

Divergent evolution(splitting)

Bonobo -Pan paniscus

Chimpanzee - Pan troglodytes

Cladogenesis is splitting or branching evolution and is illustrated in the diagram at the top. It accounts for the multitude of different species on our planet. After geographic separation, each lineage will, separately, experience anagenesis evolutionary change within a line of descent. Darwin and Wallace both recognized the importance of cladogenesis for creating the diversity of species that occur. They also appreciated that because a single population, when split into two isolated populations, would experience different environments, natural selection would lead to them being different after a period of time.

Note that because cladogenesis involves geographic separation followed by changes in one or both lineages it actually requires anagenesis - ie changes within a lineage.

Bonobos (Pan paniscus) and chimpanzees (Pan troglodytes) are two closely related species that separated from a common ancestor around 3 million years ago. Both species are confined to equatorial Africa. Major rivers seem to have been important in stimulating this cladogenetic event.

There are three recognized subspecies of chimpanzees and these too are separated by major rivers. Without further interbreeding, we might expect that the chimpanzee subspecies would evolve into separate species. Most urgently, we need to ensure that the populations survive!

[adapted from: de Waal and Lanting (1997) Bonobo: The Forgotten Ape University of California Press]

All species on Earth have a common ancestry, belonging to the one "tree of life". However, there is no reason why life couldnt have evolved independently more than once. Perhaps it did, but all the life forms we have observed (so far) belong to one tree.

[from: Hartl & Jones (1999) Essential genetics (2nd ed) Jones & Bartlett, Boston. p22]



Evolution and Human Biology 3: Evidence for evolution and natural selection Pre-reading: Relethford (9th ed) pp23-25

Perspective In his book On the origin of species, Darwin provided several lines of evidence for both natural selection and evolution. In this lecture the evidence will be examined using Darwins categories but with modern concepts and examples.

In essence, Darwin used a form of the hypothetico-deductive process (ie the scientific method) to argue his case. He had ideas (eg evolution and natural selection) which led to predictions, which he tested mainly using natural experiments (ie observations of nature, rather than laboratory experiments). For example, if natural selection occurred then we would expect to observe inherited variation (which we do). Using this method, neither Darwin nor others who have followed him, have been able to falsify the major evolutionary hypotheses. Indeed, the explanatory

power of the principles of evolution has been so strong that these hypotheses have been accorded the status of a theory - the 'theory of evolution'. Here, the word theory is used to refer to statements of principles that have been widely tested and accepted. Note that the word theory is used in two quite different ways in our language. In the formal scientific sense, it is used to describe an accepted system of ideas, laws or principles that explain observations or other phenomena (other examples include the theory of relativity, quantum theory etc). Alternatively, in non-technical usage, it is used to mean something that is merely speculation or perhaps hypothesis. In science, when we refer to the 'theory of evolution' we are using the meaning of the word 'theory' as used in its formal sense in science.

Outline 1. Domestication 2. Fossil record 3. Comparative anatomy

Homologous characters Vestigial organs

4. Geographic distribution

Terms Adaptive radiation Analogous feature Artificial selection Common ancestry Convergent evolution Domestication Evolutionary constraint Genetic code Homologous features Potassium-Argon dating Radioactive decay Radio-carbon dating Vestigial organ

Domesticated pigeons. Anyone who has visited pigeon fanciers aviaries (common until quite recently) will know that there is an enormous number of different pigeon forms. These have all been selected from a wild ancestor, the rock dove (Columbia livia, top right). This process is referred to as domestication - an example of artificial selection (selection applied by humans according to their preferences). It only differs from evolution by natural selection because humans have played a role in determining the fitness of the various forms, through their (ie human) preferences. Darwin argued that IF evolution by natural selection occurred THEN humans could become the selective agent (ie determine the fitness of types). There are many other examples including dogs, cats, farm animals and vegetables. Indeed, almost all the foods we eat, other than those that are wild-caught (e.g. some seafoods), have been altered by domestication.




Agriculture and Domestication. Almost all the foods we eat, both animal and vegetable, have been modified by artificial selection. This process began about 10-12,000 years ago when humans began to cultivate plants and tame animals. In the past few years we have developed new techniques to speed up the rate at which we can change the genetic constitution of domesticated species through the use of new technologies that allow us to direct changes in genes rather than rely on naturally occurring mutations to provide variation.


Selection experiment with mice to create large and small strains. Here two simultaneous experiments have been conducted, both beginning with the same population of mice. In one experiment, the heaviest mice were chosen in each generation to reproduce and contribute to the next generation. There was a 'response' to this selection, with a trend towards increasing average weight as the generations proceeded. In the other experiment the lightest mice were chosen to reproduce and a corresponding response was observed. This illustrates the existence of inherited variation and the ability to change the frequency of the desired phenotype (ie change the genetic constitution of the population). Note that the response will eventually slow down and stop because genetic variation will decline as the selection continues over many generations. Without genetic variation, there can be no evolution!


Timeframe for hominid fossils. If Darwin was correct, we would expect to observe anagenesis changes within a lineage over evolutionary time. This is observed in many different fossil series, including those leading to modern humans. However, it is not certain (perhaps even unlikely) that all of the fossils shown here are in a direct line to modern humans (ie are our direct ancestors).

[from: Campbell (1996) Biology. (4th ed) Benjamin Cummings, California. p657]

Left - Archaeopteryx fossil. Right - reconstruction. Archaeopteryx is often used as an example of an intermediate form ie a representative of a group that was very near a major cladistic event. In this case it is believed to be near the origin of birds, which evolved from one lineage of reptiles. Archaeopteryx has some features found in modern birds but not reptiles (eg feathers) as well as some features found in reptiles but not birds (eg teeth and a bony tail). If Darwins theory is correct, this is exactly the sort of fossil we expect to find - occasionally!




Convergent evolution (analogous features) in three marine predators. There are two quite different reasons why species may be morphologically similar. If two species have recently evolved from a common ancestor then they are likely to appear very similar. This is because they have features that were present in their recent common ancestor, and these characteristics have remained unchanged in these two species. Such features are called homologies.

Alternatively, two similar looking species may be far removed from one another in evolutionary time but, because they have very similar lifestyles, natural selection may have favoured similar phenotypes, giving them similar appearances. Sharks, porpoises (related to dolphins) and ichthyosaurs (an extinct reptile) are marine predators near the top of the food chain. They have large bodies and can swim very fast. They look very similar (though certainly not identical) yet their intermediate ancestors were quite different from one another (ultimately, of course, all species share a single common ancestor). Their external morphologies are similar because they are adapted to a very similar lifestyle feeding on fairly large fish. Natural selection for the same lifestyle has produced a similar body shape, independently, in what started out as morphologically quite different lineages. This represents convergent evolution separate lineages that were quite different but become similar because of similar lifestyles. The features that appear similar but evolved independently are called analogous characters. The theory of evolution predicts such superficial similarities.


Forelimbs of vertebrates illustrating homology. Species that share a common ancestor will have some features in common because those features were present in the common ancestor and have remained unchanged in the descendent species. The extent of these homologous features will depend upon (a) the time since the two species shared a common ancestor, as well as (b) the necessity to change the features in descendents, and (c) the ability of natural selection to make the change. Sometimes, even though they are remarkably similar, the structure may be used for quite different purposes in different species. For example, the basic structure of forelimbs in tetrapods is a single proximal bone (humerus), two intermediate bones (radius and ulna), wrist bones (carpals), and five digits (metacarpals and phalanges). This arrangement is virtually universal, with the exceptions usually being losses of bones. Different species use their limbs for a variety of purposes - legs for walking, as arms, as wings, and flippers for swimming. Of course it may be that rather than natural selection not being able to change the arrangement, it does not need to change it.

All species on Earth ultimately share a common ancestor, and there are some features shared by all species because of their common ancestry. One of these is the genetic code, most of which is identical in all species. These homologous features often represent phylogenetic constraints (evolutionary constraints) that natural selection has been unable to change (or does not need to).


Similarities between vertebrate embryos. Note the tail and gill arches in the early human embryo on the far right. Embryology reveals remarkable similarities between all vertebrates during their early development. These are examples of homologies and reflect phylogenetic constraints. Initially all these embryos start out as a single fertilized cell and would look virtually identical - at least superficially. Part of the similarity is due to this simplicity, but it is also due to the developmental process. Development is constrained by what occurred in the common ancestor leaving the embryo forced to progress through certain stages in a similar (though not identical) fashion. In essence, organisms have almost no choice but to make use of common underlying embryological patterns of their ancestors. As they further develop, of course, they come to look quite different as adults.

These drawings were made by the German biologist Ernst Haeckel (1834-1919) and are quite controversial. They contain errors. Furthermore, Haekel used them as evidence for a hypothesis that is now discredited (recapitulation). However, the drawings correctly illustrate the close anatomical similarity between the early embryonic stages of vertebrates and their divergence as they develop further.




Vestigial features are anatomical characters that have decreased in size and complexity because their original function is no longer required. Natural selection would be expected to favour them diminishing in size and functionality because that would save the energy needed to build and maintain them. We might expect that eventually these features would disappear altogether, and the only reason we observe them at all is there has not been enough time for natural selection to accomplish this. However, this may not always be the case. For example, there has been, apparently, plenty of time for natural selection to remove our appendix which we have not needed since our diet changed a very long time ago away from one that was rich in cellulose. One hypothesis is a very small appendix is deleterious because it is more prone to infection than a larger one so natural selection has not be able to completely remove it. If this is correct, it represents another example of a phylogenetic constraint. Perhaps the only way that we could get rid of the appendix is by a single mutation that deletes it entirely (without upsetting other organs and functions). This is far less likely to occur than mutations that make minor changes to its size.


Adaptive radiation. Left - Galapagos islands. Right - Beaks of some Galapagos finches. On mainland South America, finches occupy a very restricted niche as a ground dwelling, seeding eating bird. The Galapagos island finches are derived from South America but occupy a much broader range of habitats and lifestyles than finches found in South America (or anywhere else in the world). There are thirteen species of Galapagos finches, with some being tree-dwellers, some eating insects, others fruits and others nectar. There is a variety of beak sizes amongst the seed eaters. This represents an example of adaptive radiation.

Most of the time, species are restricted in what they can do (eg the foods available to them, the places for resting etc) because of competition from other species that utilize

those resources. A species that finds itself in a habitat where many different niches are unoccupied (eg the early colonizers on a new island) may have the opportunity to diversify and fill those niches. This process is called adaptive radiation. It is a flush of cladogenetic events. This can happen on a small scale such as on the Galapagos Islands when they first rose out of the sea (they are volcanic and appeared in the last 1 4 million years or so), on the scale of continents (eg the radiation of marsupials in Australia and South America), or the entire world.

In fact all of life is an adaptive radiation because the Earth was initially empty of life. The birds represent a very successful adaptive radiation utilizing flight as a means of locomotion. Mammals also represent an adaptive radiation that may have occurred with the demise of the dinosaurs (and many other species) 65 million years ago that left many niches unfilled. Most scientists, but not all, now believe that the extinction of the dinosaurs was probably a consequence of the impact of a 10km wide asteroid in Mexico and left many opportunities for those species that survived the devastation.

[from: Top - modified from Park (1996) Biological anthropology. Mayfield, California. p78. Bottom - Price (1996) Biological evolution. Saunders, Orlando. p31]

Adaptive radiation of marsupials. Today, there are two major groups of mammals - marsupials (metatherians) and placentals (eutherians). Marsupials were once spread throughout the world but extant (contemporary) species only occur in Australia, New Guinea, South America and North America (which has one endemic marsupial the opossum). All the mammals on the other continents are placentals. Mammals first evolved over 200 million years ago, but the number of species was quite small until about 65 million years ago. The mammals then diversified, probably because the dinosaurs left many niches unoccupied. The adaptive radiation of mammals occurred independently on isolated continents. The range of habitats and lifestyles of the Australian marsupials is similar to the placental mammals on other continents and so these two groups of mammals have experienced parallel but independent adaptive radiations. Consequently, comparisons of these two groups reveal many examples of convergent evolution, for example quolls and cats, thylacines and wolves etc.

Australia has many native placental mammals but, with the exception of the bats, they colonized Australia in recent times (over the last few million years) after the adaptive radiations described above.




Evolution and Human Biology 4: Evolution and life on Earth Pre-reading: Relethford (9th ed) pp86-87, pp93-98

Perspective The great strength of evolutionary theory is its predictive power. What we see in the world around us makes much more sense when we put it in an evolutionary context. However, there are many concepts associated with evolutionary theory that need to be appreciated before the full power of the theory becomes apparent. In this lecture we will consider some of these associated concepts as well as a series of common misconceptions about evolution.

The Earth is about 4.5 billion years old and the oldest known fossils are around 3.5 billion years old, so for most of the time that planet Earth has existed there has been life on it. Western Australia has a special place in these estimates because the oldest known fossils were discovered in the Pilbara and one of the earliest evolved life forms known, stromatolites, are found on our coastline.

The Earths crust is fractured into about a dozen tectonic plates made of rock about 5-100 km thick that sit on a hotter, denser and more fluid mantle. The continents form part of these plates (they are less dense so form the very tops of the plates). The plates move on the fluid mantle, so the continents also move and this is known as continental drift. For example, about 225 million years ago all continents were joined into a super continent known as Pangaea which subsequently broke into two continents Gondwana (essentially Antarctica, Australia, South America and Africa, but also parts of south Asia) and Laurasia (Eurasia and North America). The movement of continents has caused climatic change which in turn has forced species to adapt to new conditions. It has also had a marked effect upon the distribution of species. Continental drift is associated with volcanoes and earthquakes especially near the edges of the plates. The Banda Aceh tsunami on 26th December 2004 was the result of a massive earthquake at the interface of the Australian and Eurasian plates. In some places the movement was about 15 metres.

A species is a group of individuals that can interbreed (at least potentially) and produce fertile offspring, and cannot successfully breed with other groups. Humans, chimpanzees, gorillas, dogs and jarrah trees are each distinct species. Species are classified in a hierarchical system, in an analogous way to our home address (although usually written in reverse order with the equivalent of the street name written last and the country or state first). At the base of this system is a level called species and above this is the genus level. Often, in referring to an organism, we just use these two levels for example, humans are Homo sapiens (genus followed by species). There are some very specific rules used - only the first letter of the genus name is capitalized - all the other letters of the genus and species are

written in lower case. Both words are italicized, or underlined if hand-written. There are several levels above Genus. Taxonomy, the science of classification, is largely arbitrary, although many practitioners attempt to match, as far as possible, the classification with the evolutionary relationships.

No organism is perfect despite wonderful adaptations. Individuals get diseases, age and inevitably die. Why hasnt natural selection produced the perfect species with individuals that live forever? One reason is that natural selection is constrained by the variation that is available to it, and by its inability to see into the future and prepare for environmental change. As a result, there is a sense in which all organisms have limitations and inefficiencies. For example, the ductus deferens (vas deferens), which carries sperm from the testis to the penis, takes a circuitous path that makes it several times longer than it would be if it took the most direct route. This is because of evolutionary history and the inability of natural selection to produce a more efficient structure.

A key feature of natural selection is that, within these limitations, it produces an organism that maximizes reproductive success for the environment at the time in which the organism lives.

Sometimes the circumstances (ie environment) for males and females are different, and natural selection has resulted in the two sexes being quite different from one another because their needs (for reproduction) are different; the species is then said to exhibit sexual dimorphism.

The principles of evolution are widely misunderstood. Discussing many of the common misconceptions helps in understanding the theory. Evolution does not inevitably lead to greater size or complexity (although the first organisms were necessary simple and small). Nor should we try and apply evolutionary theory to social or political systems - this is known as social darwinism. In a capitalist world, making money is the key measure of success but in the Darwinian world success is only measured in terms of the number of offspring so it is inappropriate to justify the exploitation of poor or oppressed people on the basis of evolutionary theory. Furthermore, natural selection has produced altruism, cooperative behaviour and free will. Natural selection does not work for the good of the species it simply maximizes individuals reproductive success. For the same reason, it is not strictly survival of the fittest, a term not used by Darwin. Survival is necessary, but not sufficient, for reproduction.

Outline 1. The time frame of evolution 2. Continental drift 3. Species and taxonomy 4. Phylogenetic constraint 5. Sexual selection 6. Some common misconceptions



15 BY BP

0 today

Big Bang

10 Milky Way

4.5 Solar system 3.5 1st fossils

Time frame for evolution

MY BP Epoch Period Era Features 3,500 - Precambrian All major groups (fungi, algae, plants & animals) appear

590 Paleozoic (ancient life) Age of invertebrates

1st fishes & amphibians appear Ends with mass extinction of invertebrates

250 Triassic Mesozoic (middle life) Age of reptiles

1st mammals & birds appear Ends with mass extinction of dinosaurs

213 Jurassic 144

Cretaceous 65

Paleocene

Tertiary Cenozoic (recent life) Age of mammals

Radiation of mammals, birds and flowering plants

54 Eocene

37 Oligocene

24 Miocene

5 Pliocene

1.8 Pleistocene

Quaternary 0.01 Holocene (Recent) 0

Terms Big bang Chronospecies Continental drift

Tectonic plates Cyanobacteria Ductus deferens Eukaryotes Evolutionary trade-off Geological time scale

Era Period

Epoch

Gondwana Invertebrates Laurasia Macroevolution Marsupials Microevolution Pangaea Phylogenetic constraint Placentals Prokaryotes Sexual dimorphism Sexual selection

Social Darwinism Stromatolites Taxonomic levels

Kingdom Phylum Class Order Family Genus Species

Vertebrates

Stromatolites are composed of mats of single-celled cyanobacteria (once known as blue-green algae). Fossilized stromatolites have been dated to 3.5 billion years before present (BP) and are the oldest known fossilized life forms. Nonetheless, there must have been earlier, simpler life forms that were not fossilized (or as yet havent been discovered).

[from: Park (1996) Biological anthropology. Mayfield, California. p92]

The time frame for evolution. A simple representation of some major events since the beginning of the universe. Cosmologists have estimated that the universe is about 15 billion years old, having started with a big bang. Although the oldest fossils are 3.5 billion years old (except the lecturer) there must have been life forms that existed before that time because we know that stromatolites are actually quite complex organisms and cannot be representative of the very first life forms; these must have been simpler, but as they were lacking hard body parts they were unlikely to form fossils.

Geological time scale. The age of rocks are classified into a series of Eras (Precambrian, Paleozoic, Mesozoic and Cenozoic), each of which is subdivided into Periods and these are further subdivided into Epochs. The boundaries between these classifications were constructed by geologists (the whole arrangement is known as the Geological Time Scale) according to dramatic changes in the fossil record. For example, the boundary between the Mesozoic (middle life) and the Cenozoic (recent life) is at 65 million years BP (before present) and corresponds to the mass extinction of the dinosaurs that probably occurred as a result of the impact of an asteroid in Mexico which had massive effects on the environment. Like most mammals, primates radiated during the Cenozoic. Hominid evolution occurred from the Pliocene on. The genus Homo begins in the Pleistocene and the boundary between the Pleistocene and Holocene (Recent) approximately corresponds to the beginnings of domestication and agriculture.



The boundaries in the geological time scale often correspond to marked evolutionary events, especially extinctions and radiations. The scale is also used to position other major events.

There are two distinct life forms - organisms are either prokaryotes (single cell organisms without a nucleus, such as bacteria) or eukaryotes (fungi, plants and animals which have nuclei and organelles, and are often multicellular). These two groups of organisms are believed to have a common ancestor in the Precambrian, at about 2 billion years ago (ie the first eukaryotes may have arisen about 2,000 million years ago before that time there were only prokaryotes). The first vertebrates appeared at about 500 million years ago, and the first mammals at around 200 million years before present.


Continental drift. At about 225 million years BP all continents were joined into a single super continent known as Pangaea. This subsequently fractured into a large southern continent (Gondwana) and a northern one (Laurasia), and this was followed by further movements until the arrangement we see today. The plates continue to move at a rate of a few centimetres a year. At present, the Australian and Oriental plates are colliding. These two plates have very different flora and fauna due to a long separation. The Indonesian islands where these fauna and flora are now meeting is known as Wallacea, after A. R. Wallace, the co-discoverer of natural selection. Wallace is also considered the father of biogeography the study of the distribution of species in space and time.

[from: http://www.noc.soton.ac.uk/gg/classroom@sea/general_science/images/plate_history_lge.jpg]

Tectonic plates. These plates float on the Earth, a phenomenon known as continental drift. At many of the ridges in the oceans, the sea floor is spreading because lava is brought to the surface (eg the mid-Atlantic ridge). This forces the plates apart - Australia is being pushed north at the rate of a few centimetres per year due to sea-floor spreading to the south. At other junctions, the plates move towards one another, with one plate being forced under another - the Australian plate is being forced under the Eurasian plate near Sumatra and other Indonesian islands such as Bali and Timor. Plates can also slide past one another, as in western California. The figure plots earthquakes and volcanoes. These are strongly associated with the boundaries of tectonic plates.

[from: http://pubs.usgs.gov/publications/text/dynamic.html]

Continental drift has had a marked influence on the distribution and evolution of species. For example, the placental mammals (eutherians) had spread over most continents by the beginning of the Pliocene (5 million years ago), replacing other mammalian forms the marsupials (metatherians) and monotremes (prototheria - platypus and echidna). However, during this replacement period, Australia and South America were separated from all the other continents by a substantial sea barrier and were generally devoid of eutherians. Relatively recently (about 3.5 million years ago) South America and North America were joined by a land bridge (the Isthmus of Panama) giving the opportunity for many placental land mammals to colonize South America from the north. Nonetheless, many marsupials also continue to exist in South America.




The dark-shaded areas show the approximate extent of land that is currently under the sea but was exposed during the Pleistocene glaciations or Ice Ages. From the beginning of the Pleistocene (about 1.8 MY ago) there have been cycles of cold and warm periods the length of each cycle was about 100,000 years. We are at present in a warm period. During the cooler periods a large proportion of the Earths water was bound up as ice so sea levels were up to 120 metres below their current levels.

During the Ice Ages, with the changes in oceanic currents and weather patterns, East Africa became much drier. Human ancestors would have experienced their forests shrinking and this change in their environment may have been the stimulus for evolutionary adapatation.

The broken line marks Wallaces Line named after A. R. Wallace who noticed that the fauna on Bali and the land to its west was primarily Asian in origin while from Lombok to the east there was more fauna of Australian origin.

From the demise of the dinosaurs at around 65 MY before present until the beginning of the Pleistocene, the Earth was much warmer than it is today so there was little ice for most of that period (compared to the Ice Ages). This period corresponded to the adaptive radiation of the mammals.

[from: Futuyma (2005) Evolution. Sinauer, Sunderland Massachusetts, p113]

Continental drift and homology. Ratites are flightless birds including the emu, cassowary, ostrich, rhea and kiwi. Today, species are found in Australia, New Guinea, Africa, South America and New Zealand. Ratites evolved in Gondwanaland, which consisted of these landmasses as well as Antarctica and southern Asia. After Gondwanaland split up, the ratites evolved independently on the separate continents and islands. Differences evolved, but all remained flightless, the ancestral condition (an homologous feature). As a group they remain restricted to the southern continents.

[from: Futuyma (1986) Evolutionary biology (2nd ed). Sinauer, Massachusetts. p375]

Left: On the right side of this diagram, using solid lines, is shown the path of the ductus deferens (vas deferens) from the testis to the urethra via a loop over the ureter. On the left side of the diagram (again with solid lines) is shown a hypothetical duct using a more direct path.

Why is the real path so long? In our quadrupedal ancestors, the testes were near the kidneys as shown by the dashed lines. As we became bipedal and developed external testes they moved to a more inferior position. Over evolutionary time, as the testes moved position, they passed the ureter on the wrong side so that the ductus deferens was caught on the ureter. It was easier for natural selection to extend the length of the ductus deferens rather than correct its path. This inefficiency (in terms of the length of the tube) is an example of a limitation of natural selection and is sometimes referred to as a historical or phylogenetic constraint. Natural selection cannot

produce a perfect design (whatever that may mean), but only work with the structure it already has, the inherited variation that is available to it, and the conditions imposed by the environment.

Right: The gardeners problem when the hose is fully extended he can go back around the tree to continue watering, whereas natural selection cannot go "backwards" - ie make an organism less fit so that future generations would have higher fitness. The easiest solution for natural selection is to extend the length of the duct/hose.

[from: Williams (1996) Plan and purpose in nature. Phoenix, London. p194, 196]



Tetrapod limbs are another example of phylogenetic constraint, which reflect a retained homology. The common ancestor of all tetrapods had four limbs (e.g. on left) with the same basic bone structure (on the right note the similarity of the skeletal structure of humans and birds). Natural selection has been unable, or found it unnecessary, to change this basic plan, even though the limbs are used for a wide variety of purposes. This limb structure is an homology the same feature in two or more species that was present in their common ancestor. Homologies really only come to be considered constraints when they appear to be inefficient, although efficiency is hard, if not impossible, to define.

[from: Left - Lewin (1998) Principles of human evolution. Blackwell, Massachusetts. p32. Right - Young (2007) The discovery of evolution (2nd ed). Cambridge University Press p18]

Natural selection is differential reproductive success. The anatomical, physiological and behavioural features with which we are endowed are the result of natural selection to maximize reproductive success (i.e. fitness) in a particular environment and for a particular lifestyle. However, it is important to appreciate that humans and other organisms do not consciously seek, in a direct way, to maximize their own reproductive success.


We are, to a considerable extent, the result of our evolutionary history or phylogeny. Our body form, with all its anatomical features and some aspects of our behaviour have been shaped by natural selection. This is a limited process limited by what has happened before (ie phylogenetic constraint), the variation available for selection (ie what mutations arise), and the conditions at the time of selection (ie the environment).


Sexual dimorphism in gorillas. Sometimes the circumstances for males and females are different, and natural selection favours different body forms for the two sexes of a species. The most obvious examples of this are the reproductive organs and the secondary sexual characteristics. These differences arise because each sex has different needs for reproductive success (eg females must lactate, males need to make sperm, etc). In some primates and other mammals, males are larger, on average, than females. These are examples of sexual dimorphism.

Sexual dimorphism sometimes exists because males compete amongst themselves for access to females and size can be important in this competition. Because females may not compete in the same way they can afford to be smaller (being large requires more energy for the growth and maintenance of the body, so it is certainly not beneficial in all circumstances). Sexual dimorphism, in this case, reflects an evolutionary compromise or trade-off the risk for a male is injury in a fight or starvation during famine, but the benefit is better access to females and therefore potentially more offspring. Natural selection related to competition for mates that results in sexual dimorphism is usually

referred to as sexual selection. Sexual selection is not different from natural selection; it is just an arbitrarily defined category of natural selection. Bright colouration in the males of some bird species is another example of sexual dimorphism due to sexual selection.

Larger male body size compared to females is due to intra-sex competition males fighting with one another for access to females. Bright colouration in male birds is due to inter-sex competition females choose which males are successful in mating. Both of these are examples of sexual dimorphism, and examples of sexual selection.

[from: Sterry (1994) Monkeys & apes Magna]

Evolution 1Evolution and Human BiologyLectures: 1. First principles of evolution2. Charles Darwin3. Evidence for evolution and natural selection4. Evolution and life on EarthReading: Futuyma DJ (2005) Evolution. Sinauer Associates, SunderlandEvolution and Human Biology 1: First principles of evolutionPre-reading: Saladin KS (2012) Anatomy and physiology: the unity of form and function (6th ed) pp7-10.PerspectiveOutlinePreamble: (a) Resources & Rules(b) What is Human Biology?1. What is evolution?2. Some examples of evolution3. Variation4. Natural selection5. Consequences of evolutionTermsCommon ancestryDomestication (Artificial selection)EvolutionFitnessNatural selectionVariation

Evolution 2Evolution and Human Biology 2: Charles DarwinPre-reading: Relethford (9th ed) pp11-14 and pp25-30Outline1. Science, evolution, religious beliefs and pre-Darwinian thought Conflicts between science and religion How science is done Pre-Darwinian thoughts Challenges to rigidity2. Charles Darwin Darwins life Voyage of the Beagle Outline of his ideasTermsAnagenesisCladogenesisFalsificationGreat Chain of BeingScale of NatureHypothetico-deductive processTheoryUniformitarianismPeople & PlacesAristotleCopernicusGalileoHuttonLyleWallaceGalapagos IslandsTemple of Serapis[from: Moorehead (1971) Darwin and the Beagle. Penguin, Melbourne. p23][from: Moorehead (1971) Darwin and the Beagle. Penguin, Melbourne. Frontispiece and pp16-17][from: Annals of Human Biology. Taylor & Francis, London. Front cover]Alfred Russel Wallace wrote to Darwin in 1858, expressing the idea of natural selection. Wallace was a biologist collecting animals in eastern Indonesia. This is the region where two of the worlds most different faunal groups merge - Oriental and A...Note that because cladogenesis involves geographic separation followed by changes in one or both lineages it actually requires anagenesis - ie changes within a lineage.Bonobos (Pan paniscus) and chimpanzees (Pan troglodytes) are two closely related species that separated from a common ancestor around 3 million years ago. Both species are confined to equatorial Africa. Major rivers seem to have been important in st...There are three recognized subspecies of chimpanzees and these too are separated by major rivers. Without further interbreeding, we might expect that the chimpanzee subspecies would evolve into separate species. Most urgently, we need to ensure that...

Evolution 3Evolution and Human Biology 3: Evidence for evolution and natural selectionPre-reading: Relethford (9th ed) pp23-25PerspectiveOutline1. Domestication2. Fossil record3. Comparative anatomy Homologous characters Vestigial organs4. Geographic distributionTermsAdaptive radiationAnalogous featureArtificial selectionCommon ancestryConvergent evolutionDomesticationEvolutionary constraintGenetic codeHomologous featuresPotassium-Argon datingRadioactive decayRadio-carbon datingVestigial organ[from: Price (1996) Biological evolution. Saunders, Orlando. p33][from: Gary Larson The Far Side][from: Price (1996) Biological evolution. Saunders, Orlando. p11]

Evolution 4Evolution and Human Biology 4: Evolution and life on EarthPre-reading: Relethford (9th ed) pp86-87, pp93-98Outline1. The time frame of evolution2. Continental drift3. Species and taxonomy4. Phylogenetic constraint5. Sexual selection6. Some common misconceptionsTermsBig bangChronospeciesContinental driftTectonic platesCyanobacteriaDuctus deferensEukaryotesEvolutionary trade-offGeological time scaleEraPeriodEpochGondwanaInvertebratesLaurasiaMacroevolutionMarsupialsMicroevolutionPangaeaPhylogenetic constraintPlacentalsProkaryotesSexual dimorphismSexual selectionSocial DarwinismStromatolitesTaxonomic levelsKingdomPhylumClassOrderFamilyGenusSpeciesVertebrates[from: Park (1996) Biological anthropology. Mayfield, California. p92]Geological time scale. The age of rocks are classified into a series of Eras (Precambrian, Paleozoic, Mesozoic and Cenozoic), each of which is subdivided into Periods and these are further subdivided into Epochs. The boundaries between these classif...[from: Gary Larson The Far Side][from: Gary Larson The Far Side][from: Left - Lewin (1998) Principles of human evolution. Blackwell, Massachusetts. p32. Right - Young (2007) The discovery of evolution (2nd ed). Cambridge University Press p18][from: Gary Larson The Far Side][from: Gary Larson The Far Side]

/ColorImageDict > /JPEG2000ColorACSImageDict > /JPEG2000ColorImageDict > /AntiAliasGrayImages false /CropGrayImages true /GrayImageMinResolution 300 /GrayImageMinResolutionPolicy /OK /DownsampleGrayImages true /GrayImageDownsampleType /Bicubic /GrayImageResolution 300 /GrayImageDepth -1 /GrayImageMinDownsampleDepth 2 /GrayImageDownsampleThreshold 1.50000 /EncodeGrayImages true /GrayImageFilter /DCTEncode /AutoFilterGrayImages true /GrayImageAutoFilterStrategy /JPEG /GrayACSImageDict > /GrayImageDict > /JPEG2000GrayACSImageDict > /JPEG2000GrayImageDict > /AntiAliasMonoImages false /CropMonoImages true /MonoImageMinResolution 1200 /MonoImageMinResolutionPolicy /OK /DownsampleMonoImages true /MonoImageDownsampleType /Bicubic /MonoImageResolution 1200 /MonoImageDepth -1 /MonoImageDownsampleThreshold 1.50000 /EncodeMonoImages true /MonoImageFilter /CCITTFaxEncode /MonoImageDict > /AllowPSXObjects false /CheckCompliance [ /None ] /PDFX1aCheck false /PDFX3Check false /PDFXCompliantPDFOnly false /PDFXNoTrimBoxError true /PDFXTrimBoxToMediaBoxOffset [ 0.00000 0.00000 0.00000 0.00000 ] /PDFXSetBleedBoxToMediaBox true /PDFXBleedBoxToTrimBoxOffset [ 0.00000 0.00000 0.00000 0.00000 ] /PDFXOutputIntentProfile () /PDFXOutputConditionIdentifier () /PDFXOutputCondition () /PDFXRegistryName () /PDFXTrapped /False

/CreateJDFFile false /Description > /Namespace [ (Adobe) (Common) (1.0) ] /OtherNamespaces [ > /FormElements false /GenerateStructure false /IncludeBookmarks false /IncludeHyperlinks false /IncludeInteractive false /IncludeLayers false /IncludeProfiles false /MultimediaHandling /UseObjectSettings /Namespace [ (Adobe) (CreativeSuite) (2.0) ] /PDFXOutputIntentProfileSelector /DocumentCMYK /PreserveEditing true /UntaggedCMYKHandling /LeaveUntagged /UntaggedRGBHandling /UseDocumentProfile /UseDocumentBleed false >> ]>> setdistillerparams> setpagedevice







Date post:	19-Oct-2015
Category:	Documents
Upload:	mylesdennis2
View:	13 times
Download:	0 times

01 Evolution 1-4

Documents