Tuesday, 16 March 2010

Countering Creationism I: Our Ancestry

I seem to have developed something of a reputation amongst people who know me for being fiercely atheist. I get linked fairly frequently to various sources of creationist bullshit and fake science. Most of these are message boards or other similar things, and I've wasted a lot of time arguing with people who have been completely blinded by creationist viewpoints and arguments. 

What's really annoying is how much of it is just completely wrong. I can tolerate people believing in a God because ultimately there's never going to be any proof God doesn't exist. However, there's an absolute shit ton of proof for the big bang and evolution, especially the latter. All this evidence seems to have no impact on the majority of creationists, either because they don't understand the implications properly, or they've never seen it in the first place. 

The other thing I've noticed is that a lot of the creationist arguments seem to be pretty much identical. It's like there's a single source of creationist bullshit that's spreading itself out to everyone. All of these flawed arguments, all of these completely false claims are repeated over and over by various different creationists. I find that I don't have that many arguments, more I'm just having the same few over and over again. So, rather than have the same arguments over and over, I'm writing a series of blog posts for reference, because it should hopefully be a more effective solution and save me a lot of time.

A phrase that gets banded around a lot in religious debate is that humans "descended from monkeys". While from an evolutionary perspective this statement isn't necessarily incorrect, it's definitely misleading. It leads to fundamentally incorrect conclusions, and various bullshit creationist questions like "if we descended from monkeys, why are they still around?". If you're going to be picky, humans didn't descend from monkeys, because that's not how evolution works.

The nature of evolution and natural selection means it's very difficult for a species to continue unaltered. The notion that we "descended from monkeys" implies that a few tens of thousands of years ago there were only monkeys, that there was a new species that branched off and eventually became modern man, while the monkeys continued as they were until the present day. Evolution tends not to work in this way. Even in the same species and lineage, the actual individuals are constantly changing. The evolution family tree does not work in a way that has main branches with several other ones splitting off, like a fir tree. It works far more in a fractal manner. If you were to draw the network of species over time, it would look something like this:

It's very difficult there to single out any of the edge branches as being the main descendent from the original single main one. In practice the tree isn't quite as symmetric or perfect as that, and there'd obviously be millions and millions of branches, but that's just to demonstrate my point.

We did not descend from chimpanzees, gorillas or any other modern ape. We are merely 'cousins' with those species, and our original descendent was something else entirely. Our original descendent doesn't exist as a species any more. Humans are not a branch from the main line of monkeys, more that humans and all the different monkey species are various branches that all lead back to the same common ancestor species. It's totally inaccurate to say we descended from monkeys, more we descended from a totally different species that would probably resemble modern apes more than modern humans, but ultimately is totally separate from both, and didn't closely resemble either.

This fractal analogy applies to all species. You can't take just any two modern species and say one is descended from the other. It's almost always the case that the two share an ancestor that is neither one nor the other, but somewhere in between. Because of the way the evolutionary tree works you can also do this for any two animals, no matter how far apart. Humans and monkeys share an ancestor, but so do humans and rabbits. You might have to go back a lot further towards the trunk of the tree than you do for monkeys to get there, but there's going to be a point where it branches into two, and one branch contains rabbits somewhere at the end, and the other contains humans (and both branches obviously contain a crapload of other species as well). All the species around today link back to common ancestors at some point, which usually isn't alive, it's just a matter of how far back in time you have to go before you get to it.

It's a fairly simple concept, and it seems that quite a few people, supporting of both creationism and evolution don't actually understand that this is how species change and evolve. It's why there's such a diverse range of species alive at this point in time, and why it's not quite so straight forward to link them all together, because none of the intermediate species are alive right now. We did descend from something you'd probably call a monkey if you saw it today, but you're not going to see it today because that species has itself branched out and evolved into modern chimpanzees and the like.

4 comments:

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  2. A species having mutated children that are able to reproduce does not mean the parent species will die out per se. it happens a lot yes, but spiecies A and it's ancestor B can indeed coexist... If the offspring is not a threat to the existence of the ancestor (for whatever reason, biological or environmental) there is no evolutionary reason for it to die out. In case of our "Monkey business" here, yes, our common ancestor is probably extinct :D

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  3. You're right, there are enough species around today that are regarded as "living fossils" because they're pretty much genetically identical to their ancestors living tens of thousands of years ago.

    I should probably tweak the entry a bit:

    "You can't take any two modern species and say one is descended from the other. It's almost always the case that the two share an ancestor that is neither one nor the other, but somewhere in between."

    First sentence there is wrong to say "any", second sentence is correct to say "almost always the case". I'll change it.

    Either way, for human evolution, which is all most people really seem to care about, our parent species are either no longer alive, or are yet to be discovered, with the latter seeming far more likely.

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