Friday, 24 June 2011

The myth of half-humans

A christian (creationist) friend asked me some questions about evolution and on this occasion I felt able to give an answer!

If we evolved from say, apes or something similar, then why is it that we have gone backwards in some areas?  Babies, for example, can't fend for themselves at all, but baby apes/gorillas develop much quicker to be able to fend a little for themselves.

Also, where are the half-ape/half-humans now and the half whatever came before dogs and half dogs etc?  I am sure there is an answer to this, but just wondering what it is.

The apes question is a good one, commonly asked and not altogether silly.  The point is that we did not evolve from say chimpanzees or bonobos or gorillas any more than any of them evolved from us.  All these species have a niche in the world where it is actually pretty good to have their individual characteristics.  We had a common ancestor with bonobos and chimps most recently (6 millions years ago if I remember correctly, with them branching apart from each other after that).  We had a common ancestor with gorillas a little earlier, orangutans a little earlier than that.

The shared common ancestor at each branching point in the family tree is now extinct, but has led to today's different species.  That's why there are no intermediate forms alive today, and there never have been half-ape/half-humans.

It is also worth noting that evolution does not 'plan'.  Our ancestors were no more trying to become human than we are trying to become something even more advanced.  Evolution is the non-random survival of randomly-produced variations.

There is nothing to say that evolution produces continuous improvement, but if it does it there is nothing to say that all features improve at the same time (if at all).  Using your example, the relatively high dependency of our infants is more than offset by their final intelligence, and what counts is their ability to reach breeding age more than the route they take to get there.

Did that make sense?


Little Miss Joey said...

Yes, it did.
As I see it, you are right; each species occupies a niche and it's its ability to survive within that niche that dictates its evolutionary path.
Babies may not have learned to fend for themselves as it were, but they have evolved to be adorable to most adults who can ultimately take care of them. They cry and get fed, they cry and get changed, they cry and get anything really; if that's not the ultimate intelligence... well...

Kenny Wyland said...

"Babies, for example, can't fend for themselves at all, but baby apes/gorillas develop much quicker to be able to fend a little for themselves."

Just for the record, this comparison sort of misses a common ground. The first part is about human infants being helpless and the second part is about primate infants developing faster... but it ignores the fact that primate infants are also completely helpless when born.

Gorilla infants are able to walk on their own around 8ish months, while Human infants are solidly walking after 14ish months. The Gorilla infants are _definitely_ developing faster, in terms of walking, than human infants but both are born completely helpless and require the mother to protect and nurse them.