Somewhat inspired by the ‘GordyR’s guide to bodybuilding’, I have decided to make a thread which will help educate some forum members on some misunderstandings they have about the theory of evolution. Whilst not being a totally exhausting guide, it will allow those who wish to ask questions the chance to have them explained, and I can update the OP(s) accordingly. Of course, I am far from a professor in the subject, and this material has been pulled from the works of Professor Gareth Jones and Dr. Arthur Goldsmith from the University of Bristol, and I would like to give them all the credit! This guide is split into three sections, titled:
An Evolutionary Overview: What are we trying to make sense of? What evidence is there for evolution? How is it occurring?
Misconceptions about evolution: Your arguments that evolution isn’t occurring are disproved here. Also, the myths of ‘devolution’, ‘statistical chance’ and other poor terminology are corrected here. This is probably the most interesting section, so feel free to read this first.
Evolution in action: For those interested in learning evolution in some greater detail. Also a brief insight of how life might have evolved.
I hope this is at least an interesting read, and I think everyone that does will learn many things they did not previously know. If reading about bizarre whales with legs sounds intriguing then grab a cuppa and a donut and read on….
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An Evolutionary Overview:
First off, it is best to explain what we are trying to make sense of here. Throughout history, humans have struggled to explain what they see around them in terms of living organisms. Firstly, why is there so much complexity? Living things are incredibly complex, and could not have originated by chance. The information content of a single human cell alone is equivalent to all 30 volumes of the Encyclopedia Britannica (A considerably hefty read).
Why is there so much diversity? Why are there so many different forms of a single species, let alone all the different species of butterfly on the planet? Why not just one all-purpose butterfly?
Why is there a seemingly apparent design? Living things show amazing engineering. Different species in different environments have different, and seemingly carefully designed, strategies for surviving and reproducing. Check out these surprisingly sneaky Giraffes:
Before the theory of evolution, the apparent design of living things was taken as evidence of a designer, i.e. a God. Quite a reasonable assumption really – nowadays if you see a carefully designed machine then you know someone must have designed it.
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So what evidence is there for evolution occurring?
Anatomy:
Organisms share underlying similarities even when they are superficially different and have different lifestyles. e.g. the pentadactyl limb:
All of these examples show the pentadactyl limb in different organisms. This consists of the same bones in different proportions. Why is this so? Even more strangely, why do whales have hip bones but no rear legs? This is also true for some snakes inc. boas and pythons and they represent artifacts of the evolutionary process (more later).
Embryology:
Vertebrate embryos share underlying similarities even when the adults are very different (shown below). Why should human embryos show gill pouches during development? Why should the 3 bones of the middle ear develop from the same bones as the jaws of a reptile? More later.
EDIT - The gill pouches example is now believed to be an error from early microscopy studies, and as such should be overlooked as evidence for evolution.
Palaeontology:
Similar evidence to comparative anatomy, but with the dimension ‘time’ added as well. Why do fossils exist? Why are fossils in recent strata like living animals, but ones from
older (deeper) strata progressively more different? Darwin noted that fossil armadillos were very similar (though much larger) than present-day species. Why are there fossils of extinct animals at all, if all species were created at once a few thousand years ago?
Here is an example from fossil horses:
The oldest fossils in the deepest strata don’t look very like horses, but as you move up the rock layers to more recent fossils, they become progressively more horse-like. They become progressively larger, and note the loss of digits at the end of the leg bones.
Biogeography:
Similar evidence to comparative anatomy, but with the dimension ‘space’ added as well. Why are the finches on the Galapagos all similar, even though they lead different lifestyles? Why do animals and plants on one continent tend to be similar to each other (and the fossils there), yet differ from animals in similar habitats on other continents?
Taxonomy:
Why do all organisms fall into hierarchical categories?
Molecular Evidence:
Perhaps the strongest set of evidence, this has only been recently discovered as molecular techniques have become available. Why is genetic material more conserved between closely related species? This is possible to observe as DNA sequence, and also amino acid sequence. Whilst I won’t beat about this too much as it gets a bit technical, this is based on the following:
1) Nuclear and organelle genomes evolve at different rates. Useful for study purposes
2)Non-coding DNA evolves faster than coding DNA due to different functional constraints
3) Non-coding DNA can mutate without imposing any selective cost on its host. Synonymous changes accumulate faster than non-synonymous changes.
-------------------------------------------------------
These 6 lines of evidence all make sense if organisms share a common ancestry through evolution. So what is the mechanism?
Natural Selection:
If you have:
- Heritable genetic variation between individuals
- Overproduction of offspring
- Struggle for existence
Then you must get:
- Generation by generation increase in the (heritable) traits that aid survival and reproduction.
If the three basic assumptions hold true, it MUST happen. Also it explains the fit, or adaptedness, of organisms to their environment. It explains apparent design, without needing a designer. We can test three assumptions one by one:
Heritable variation:
How did Darwin persuade people that many of the differences between individuals are heritable, when genetics hadn’t been invented as a subject? Well, although he didn’t know the mechanism of inheritance, it was in fact easy to persuade people that heredity ‘happened’. First, family resemblances are obvious to everyone. But more importantly, Darwin did a lot of research on animal breeding – artificial selection. This clearly shows that heredity happens, but it also shows that animals can be changed through systematic breeding – i.e. particular inherited traits can be selected for. It also shows that large changes can happen in a short space of time. St. Bernards and Pekinese have been produced from the same stock of dogs in a few 100 years, just by differential spread of heritable traits. Broccoli, Brussel sprouts, cabbage and cauliflower have all been bred from wild mustard.
Overproduction of offspring:
Darwin was impressed by the work of Malthus, an economist, who noted that unrestricted populations grow exponentially (2 parents have 2 children who have 2 children etc.), but food supplies can only grow arithmetically (if you’re lucky). So there will always be competition for food – a ‘struggle for existence’.
----------------------------------------------------------------
The ‘Modern Synthesis’ (1950s):
We now consider evolution as that following:
1) Gradual evolution results from small genetic changes that are acted upon by natural selection.
2) The origin of species and higher taxa (i.e. ‘macroevolution’) can be explained in terms of natural selection acting on individuals (microevolution).
An Evolutionary Overview: What are we trying to make sense of? What evidence is there for evolution? How is it occurring?
Misconceptions about evolution: Your arguments that evolution isn’t occurring are disproved here. Also, the myths of ‘devolution’, ‘statistical chance’ and other poor terminology are corrected here. This is probably the most interesting section, so feel free to read this first.
Evolution in action: For those interested in learning evolution in some greater detail. Also a brief insight of how life might have evolved.
I hope this is at least an interesting read, and I think everyone that does will learn many things they did not previously know. If reading about bizarre whales with legs sounds intriguing then grab a cuppa and a donut and read on….
-----------------------------------------------------
An Evolutionary Overview:
First off, it is best to explain what we are trying to make sense of here. Throughout history, humans have struggled to explain what they see around them in terms of living organisms. Firstly, why is there so much complexity? Living things are incredibly complex, and could not have originated by chance. The information content of a single human cell alone is equivalent to all 30 volumes of the Encyclopedia Britannica (A considerably hefty read).
Why is there so much diversity? Why are there so many different forms of a single species, let alone all the different species of butterfly on the planet? Why not just one all-purpose butterfly?
Why is there a seemingly apparent design? Living things show amazing engineering. Different species in different environments have different, and seemingly carefully designed, strategies for surviving and reproducing. Check out these surprisingly sneaky Giraffes:

Before the theory of evolution, the apparent design of living things was taken as evidence of a designer, i.e. a God. Quite a reasonable assumption really – nowadays if you see a carefully designed machine then you know someone must have designed it.
-----------------------------------------------------------------
So what evidence is there for evolution occurring?
Anatomy:
Organisms share underlying similarities even when they are superficially different and have different lifestyles. e.g. the pentadactyl limb:

All of these examples show the pentadactyl limb in different organisms. This consists of the same bones in different proportions. Why is this so? Even more strangely, why do whales have hip bones but no rear legs? This is also true for some snakes inc. boas and pythons and they represent artifacts of the evolutionary process (more later).

Embryology:
Vertebrate embryos share underlying similarities even when the adults are very different (shown below). Why should human embryos show gill pouches during development? Why should the 3 bones of the middle ear develop from the same bones as the jaws of a reptile? More later.
EDIT - The gill pouches example is now believed to be an error from early microscopy studies, and as such should be overlooked as evidence for evolution.

Palaeontology:
Similar evidence to comparative anatomy, but with the dimension ‘time’ added as well. Why do fossils exist? Why are fossils in recent strata like living animals, but ones from
older (deeper) strata progressively more different? Darwin noted that fossil armadillos were very similar (though much larger) than present-day species. Why are there fossils of extinct animals at all, if all species were created at once a few thousand years ago?
Here is an example from fossil horses:

The oldest fossils in the deepest strata don’t look very like horses, but as you move up the rock layers to more recent fossils, they become progressively more horse-like. They become progressively larger, and note the loss of digits at the end of the leg bones.
Biogeography:
Similar evidence to comparative anatomy, but with the dimension ‘space’ added as well. Why are the finches on the Galapagos all similar, even though they lead different lifestyles? Why do animals and plants on one continent tend to be similar to each other (and the fossils there), yet differ from animals in similar habitats on other continents?
Taxonomy:
Why do all organisms fall into hierarchical categories?
Molecular Evidence:
Perhaps the strongest set of evidence, this has only been recently discovered as molecular techniques have become available. Why is genetic material more conserved between closely related species? This is possible to observe as DNA sequence, and also amino acid sequence. Whilst I won’t beat about this too much as it gets a bit technical, this is based on the following:
1) Nuclear and organelle genomes evolve at different rates. Useful for study purposes
2)Non-coding DNA evolves faster than coding DNA due to different functional constraints
3) Non-coding DNA can mutate without imposing any selective cost on its host. Synonymous changes accumulate faster than non-synonymous changes.
-------------------------------------------------------
These 6 lines of evidence all make sense if organisms share a common ancestry through evolution. So what is the mechanism?
Natural Selection:
If you have:
- Heritable genetic variation between individuals
- Overproduction of offspring
- Struggle for existence
Then you must get:
- Generation by generation increase in the (heritable) traits that aid survival and reproduction.
If the three basic assumptions hold true, it MUST happen. Also it explains the fit, or adaptedness, of organisms to their environment. It explains apparent design, without needing a designer. We can test three assumptions one by one:
Heritable variation:
How did Darwin persuade people that many of the differences between individuals are heritable, when genetics hadn’t been invented as a subject? Well, although he didn’t know the mechanism of inheritance, it was in fact easy to persuade people that heredity ‘happened’. First, family resemblances are obvious to everyone. But more importantly, Darwin did a lot of research on animal breeding – artificial selection. This clearly shows that heredity happens, but it also shows that animals can be changed through systematic breeding – i.e. particular inherited traits can be selected for. It also shows that large changes can happen in a short space of time. St. Bernards and Pekinese have been produced from the same stock of dogs in a few 100 years, just by differential spread of heritable traits. Broccoli, Brussel sprouts, cabbage and cauliflower have all been bred from wild mustard.
Overproduction of offspring:
Darwin was impressed by the work of Malthus, an economist, who noted that unrestricted populations grow exponentially (2 parents have 2 children who have 2 children etc.), but food supplies can only grow arithmetically (if you’re lucky). So there will always be competition for food – a ‘struggle for existence’.
----------------------------------------------------------------
The ‘Modern Synthesis’ (1950s):
We now consider evolution as that following:
1) Gradual evolution results from small genetic changes that are acted upon by natural selection.
2) The origin of species and higher taxa (i.e. ‘macroevolution’) can be explained in terms of natural selection acting on individuals (microevolution).
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