Saturday, May 30, 2009

Bad reason #2 – Monkeys don’t give birth to people

This is the second article in my series of 10 bad reasons to reject evolution, this post deals with the objection that "We have never seen a monkey give birth to a human".

This is a common one, often you hear people say things like "viruses are one thing but you never see a dog giving birth to a cat", so what it behind this objection and why is it bad?

The root of this objection is seated in ignorance; the person making it clearly does not (or does not want to) understand what the theory of evolution actually proposes in order to explain speciation (the changing of one species into another) Asking to see a monkey birth a human is a somewhat ridiculous requirement because it is clearly impossible and that's not what evolution says anyway. A classic "straw man" argument and a favourite among young earth creationists.

What evolution actually says is that speciation normally occurs over vast periods of time and in tiny cumulative increments, it is driven at the genetic level i.e. it is genes that are changing, which in turn cause bodies to gradually change. However evolution is not a random process, it is constantly guided by natural selection. Only useful changes (or adaptations) survive and in turn these successful changes become the majority in a population of genes (or a gene pool) the benchmark for the selection process is "fitness" or how successful will an individual be at living long enough in its environment to reproduce and therefore pass on those genes to the next generation.

The definition of a species is a group of animals that can interbreed, so a good question would be how many changes are needed before a new species is created? This is a complex subject but fortunately we have some excellent real-world examples that show the process but in living species rather than backwards over time. There is a species of gull that lives around the Arctic Circle, in the UK we call it the "herring gull" it is a big white bird with a grey back and is quite common. However, as we move westward towards Greenland and the American continent we still see the herring gull however it changes slightly in size and colour, over there it is called the "American Herring Gull", as we continue across Canada and into Alaska we still see our gull but it changes subtly as we go, then across into Russia we see more and more changes until we get all the way back to Scandinavia and the UK where we end up with a Gull that is quite different from our original Herring gull and is called the Lesser Black Backed Gull and is now a different species (i.e. it does not interbreed with Herring gulls). At every point in this circle the gulls in proximity to each other breed together quite happily however as the distance and the changes accumulate eventually there is a tipping point and the resultant species becomes distinct.

This is called a "ring species" and represents a huge problem for people who don't believe that evolution can create new species, all that distinguishes a ring species from two separate species is the existence of the connecting gull populations, should there ever be a natural disaster (like a new virus for example) and a segment of the ring vanishes then we will have two distinct species.


Elizabeth said...

I didn't know any of that. How interesting. You should teach after you get out of the AI biz.

Steve Borthwick said...

You never know!