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The descent of woman

October 3, 2011

Quick caveat no. 1:  Atheism and evolution are not the same thing.  You can be a Christian and accept evolutionary theory (as both the Catholic & Anglican churches do); you can be an atheist and either not know or not care about evolution, or actively disagree with it (see i.e. Raelians, or Buddhists, both of which don’t involve God-belief).

So this is an interesting sideline to our discussion, but we’re no longer talking about atheism as such.

Quick caveat no. 2:  I am no sort of expert on evolution, having GCSE biology and one year of undergrad Medicine to my name.  Anything I know about this is through books and general knowledge, not through expertise.


Having said that, back to the meat of the discussion!

Sexual selection

As Ben mentioned in the comments to the previous two posts, sexual selection also happens.

It’s part of my first category example – things which benefit the animal by making it easier for that animal to attract a mate and to reproduce.  It’s a factor in any species which has mate selection (rather than having indiscriminate fertilisation, for example).  Here’s a nice starter summary:

One of the interesting things about sexual selection is that it seems to operate on a more-is-better mechanism.  It leads to things like peacock tails, which are objectively ridiculous and a big disadvantage to the individual bird – because peahens prefer mates with good tails, and have no upper limit for defining a good tail.  Once the peahens have such a preference, selection pressures lead further and further in the same direction, limited only by the health of the animal.

Evolution is mindless

You ask why the giraffe’s ‘long-neck’ niche hasn’t come up more often, and Ben has answered that in part (this link is really interesting: )

However, the point I’d like to focus on here is that evolution is very much dependent on contingency.  Mutations are random within certain parameters, and mutations only prosper if they arise during a situation which they are well fitted for (no good to evolve a white coat for camoflage if you live in an area with no snow & nothing else white!)

So whether a particular branch in the evolutionary tree happens, or doesn’t happen, is totally dependent on the very particular circumstances prevailing at the time.  A particular mutation might be beneficial to the animal – but might not prosper anyway because the particular area that population was in got flooded out.  A mutation which makes an animal easier to spot in its habitat might persevere anyway if the predators are all dead.

It does happen, in fact, that particular traits may be advantageous and disadvantageous in different circumstances.  There are lovely experimental examples of that in this book: The Beak of the Finch by Jonathan Weiner (click for Amazon link).  This recounts a set of population studies of finches in the Galapagos Islands, and how their numbers and characteristics changed as a response to different climactic conditions.  Basically, one year would be dry, and would favour finches with a particular beak type which could access a particular nut.  Those finches would survive and breed, and that beak type would then become much more common.  However, a year later, the weather conditions would be totally different, and favour a different beak type.  So evolutionary pressures buffet the finch population in all directions.  By watching over a long time period you can see trends – but next year still might be totally different.

The descent of humans

You asked about humans having large numbers of children, and whether it is or is not beneficial from an evolutionary point of view.

Grandchildren are the markers of reproductive success, as I’m sure you’ll agree.  Achieving grandchildren proves not just that you have reproduced yourself, but that your children are healthy and fertile and have interbred successfully with other humans.

However, there is more than one way to get to that point.  One way is to have lots of kids, half of whom will die, and another is to have two kids and pour everything you have into protecting and helping them.  Either one of these works, but only if the circumstances are right.  In a hardscrabble hand-to-mouth landscape, strategy one works, and in an intensively farmed and prosperous landscape, strategy two works.

But we’re also stuck in a Tragedy of the Commons setup here.  If I don’t have kids, my genes don’t get passed down and I’m an evolutionary dead end.  So the person who refrains from having kids doesn’t benefit in evolutionary terms from their contribution to reducing overpopulation.  The person who ignores the problem and goes on to breed does get to pass their genes down.

Trees of life and directions of evolution

The short answer to this question is that evolution has no mind, and also has no direction.  More complex species do well in some circumstances, and amoeba and cockroaches in others.  The process of evolution allows complexity to arise, but does not require it.

This was a misapprehension in certain early interpretations of the theory, and led to horrors like eugenics (or like garden-variety racism and the White Man’s Burden).

As to whether more complexity is better, or whether we are ‘higher’ life forms than animals, that just begs the question of how we measure value.  Is a human more or less valuable than a rat?  We might think so, but no doubt any rat which could express a view would think differently.

In evolutionary terms, the ‘best’ species is simply the one which survives and reproduces most successfully.

I like humans myself, but then I am one and am no doubt biased.

I’m not sure I understood your question about the whales, so I’ll leave that one.

Dead ends and transitional species

I don’t know how many of the current species will turn out to be dead ends.  That can only be known afterwards – if a species becomes extinct it was a dead end, and if it doesn’t it wasn’t, yet.

Likewise, every species and every adaptation we see now is a potential transitional step on the way to something else.  But we don’t know and can’t know which ones, until it happens.

You can go to the Natural History Museum and look at skeletons which were transitional steps on the way to humans, or horses.  But you can also go and look at dinosaurs which dead-ended spectacularly, or at dodos.

If the world had been somewhat different, humans might never have evolved, and dodos might have survived.  But this world is the one which actually happened.

Brief note on atheism

Yes, there are different groups of atheists.  Technically I’m an agnostic (weak) atheist, and more of a Gnu Atheist than otherwise.  However, we aren’t like religious groups in terms of banding together.  And discussions between groups of atheists are more of an ongoing argument than anything else.

But in terms of organising my social life I’m more likely to hang out with people who enjoy dancing or artwork or weightlifting or working for social justice, rather than to hang out with people based on their religion or otherwise.

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