Originally Posted by 3rdvogon

There are some significant features about humans and our past.

Geology and Climate history suggests that we had to adapt to a new environment or contract or become extinct. We had to transform from being a tree dweller into a ground dwelling animal. The fossil record now suggests that there were a number of different branches of hominid that started to evolve this way. Some got bigger and stronger some stayed small. Some evolved to eat tough foods that would be difficult for humans like us to cope with and some followed a more diverse diet.

All of this suggested that evolution did what it always does allow variations to try and fill new environmental niches and those variations that make a success of it go on those that don't die out. Very often it is the most highly specialised species that are the first to become extinct, it is the generalists that are more versatile that go on. Evolution has never been the survival of the fittest but the survival of the most adaptable.

The one thing you can say about the human physical form is that it is pretty useless at a lot of things other animals with different body forms do much better. We cannot run as fast as most ground dwelling animals but we can climb trees and rockfaces better than most of them, though not as well as apes or monkeys. We can swim on the surface of the water and we can dive below the surface much better than most other mammals save those that have specifically evolved for an aquatic life (how many dogs, cows, horses or monkeys can swim down to a depth of 20 feet on one lungfull of air, humans can do this). The human is the classic "Jack of all trades (except flying) and master of none". However there was a price for all this versatility and this is we were fairly vulnerable to any more specialised predator that happened to be around. The only things we had to ensure our survival were hands which were freed from walking and our brains to make our hands do some new. If ever there was an evolutionary incentive to develop intelligence to make full use of those adaptable devices on the ends of our arms that was it. And once we started to do that the rate of progress towards improving our survival was far faster than any evolutionary change through bodily adaptation could deliver.

Put simply when the first hominid found that a well aimed rock hurled at a leopard and striking it on the nose was a good way of not becoming catfood you can be sure lots of other hominids picked up on that example and it would deliver positive results far quicker than waiting for generations of hominids to evolve with longer legs to outrun leopards. The brain hand combination combined with need to survive in an environment not suited to a slow moving tree climber would have been a powerful force.