Biological Evolution is a concept always associated with Charles Darwin. Like Newton, Darwin stood on the shoulders of giants, particularly Charles Lyell, who in 1830 published a book called Principles of Geology. In it he showed the evidence known then that showed that even mountains wore down, islands appeared and other changes occurred albeit very slightly, so that it took a long time for a large change to occur.
Charles Darwin was taking theology then and knew how controversial that idea was among academics never mind ordinary people, even with the evidence the Lyell had.
When Darwin graduated he was offered a place on the exploratory ship Beaglel After fighting with his father who wished him to become the local vicar, he took the offered place on the voyage which was to take 5 years. It was on that voyage that Darwin saw and recorded that not only geology changed with time but so did plants and animals. And when he arrived back in England he had a lot of evidence. But he did not want to publish because how fierce he expected the controversy to be. However
one day he got a letter from a man he often wrote to, an Alfred Wallace, who independently came up with the theory of evolution, and revealed it to Darwin in that letter. Darwin then did publish his evidence and the theory of evolution, but gave Wallace full credit for arriving at similiar conclusions with independent data. The ideas these men had that tied together the change in animals and plants they saw as they voyaged over the world are these:
Animals and plants do change over time, slowly compared with lifetimes of a member of a species.
The changes arise because offspring are slightly different from their parents. This is called genetic variation.
Changes which help the offspring deal with their environment better, and leads to more offspring of their own, create over generations a permanent change in the species. This process is called natural selection.
Darwin (and Wallace agreed) that if one change occurred in a member of a species, then all the changes consistent with that change would also occur at the same time, or within a few generations. Both gentlemen were wrong, but it was just a guess on their part, unlike the other points there was no evidence for this. It was a wishful thought. It made the idea of change of one species into another easier for them to believe.
As an example of evolution, take the climatic changes that occurred in east Africa, starting around 15,000,000 years ago. As the east African climate became dryer and cooler, the annual amount of rainfall decreased a lot.
Less rain meant few trees could grow, and the air was cooler so some animal and plant species died out.
The thick forests thinned out into clumps of trees separated by distanced measured in hundreds of meters.
The animals that lived survived by changing their behavior. Most of the apes moved out of the area where trees were far apart migrating back to jungle areas. Those apes that stayed would move from one cluster of trees to another in troops. The troops had to climb out of one set of trees on to the dry grasslands and walk to the next tree cluster, and climb into it. Sometimes they would have to run, since predators like lions, and opportunists like jackels and hyenas would attacked troops of apes on the move. Some people have suggested this was why the apes started to stand upright. It is easier to see over the grass. That was important to help spot where to go, and to spot predators. But the most potent reason for moving upright
is that it takes less energy to walk upright than it does to walk along on all four limbs. Of course these apes were not structured like humans at that time, but any variation in the offspring that took less energy on the hiking between tree clusters meant more energy to eat and reproduce, so there would be more children with these variations in the offspring, and within a five generations the change would be in most of the offspring. Each change in the anatomy of the apes toward bipedal locomotion would lead to further changes also benefitting survival and the ability to reproduce. It is slow, and it is uncertain, since the changes do not have to result in survival, just increase the chance of it.
Enough such variations reproducing generation by generation would lead a quadripedal ape species to an efficiently structured bipedal walking species. The fossil record confirms that apes with one of the structural changes appears before one with that change and another. But as mentioned else where, the fossil records for actual human like apes is very small, so the evidence although all one way, is not huge.
But in this relatively small number of usually incomplete skeletons the evidence built up that there was at least one ape that was hominoid: Australopithacus Africanus (australo=southern, pithacus=ape, Africanus=from Africa) that Raymond Dart, a South African, discovered in 1924 in a place called Tuang. Generally most paleontologists denounced his discovery, in the main because the ape was not human enough for their tastes, and it was found in Africa whereas they wanted one found in Europe. Soon after an 'ape' man was found in Piltdown England. The Piltdown was ape like human, and was proclaimed as the 'missing link' generally. By 1949 Piltdown man was realized to be a hoax, and fake created by who knows, and the A. Africanus
was dated at 2.5 million years.
By the mid 1970's there were several more humanoids found as will be described in other pages.
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