Proteins, Apes & Us (Introduction)

by dhw, Monday, April 16, 2012, 17:07 (4582 days ago) @ David Turell

DAVID: The first hominins were tree-dwelling and entered the savannah when their uprightness allowed it. Key alteration in evolution theory: Upright BEFORE savannah.-dhw: However, supposing the innovation (i.e. the mutation to uprightness) was not random but was a direct response to environmental pressure? Then we have a very different scenario. As I've suggested in earlier posts, one or more localized events in isolated areas might have destroyed the forests and changed them into savannahs. In order to survive, the monkeys HAD to come down from the trees. -DAVID: And having to stoop over to walk on their knuckles how would that work in the savannah? The arms remained long until Lucy at two-three million years ago. You must think of whole body adaptations. The fossil hunters also study paleoenvironment. No one has proposed your scenario of an earlier savannah. I think your thinking has taken you down a rabbit hole. Granted your reasoning is reasonable, but, if we can trust the science, it didn't happen your way.-Can we trust the science? We have a whole thread now devoted to that very subject. Besides, what science? Is there any scientific consensus on what happened? How do you know that Lucy was the first short-armed hominid? Is the fossil record complete? Even Lucy's locomotion is a matter of controversy:-Wikipedia: There is considerable debate regarding the locomotor behaviour of A. afarensis. Some believe that A. afarensis was almost exclusively bipedal, while others believe that the creatures were partly arboreal. The anatomy of the hands, feet and shoulder joints in many ways favour the latter interpretation.-But more to the point, you have argued that the first hominins went down into the savannah after a mutation that led to uprightness. Are you now suggesting that their uprightness was also accompanied by short arms? Clearly not if Lucy really was the first to have short arms! How upright is upright? All the scenarios are based on the same premise that a degree of uprightness conveyed an advantage. No matter whether it came via a random (or divinely planned) mutation or via an adaptation to new living conditions, the rest of the body would still have had to adapt to the new position (= your whole body adaptations). There is no way round this development if we believe in common descent. I'm pleased that you find my reasoning reasonable, because your alternative seems to me less reasonable: a chance or pre-planned mutation which leads the ex-monkey (still with long arms) to look for a new environment, versus my change in the environment which forces monkeys to adapt or die.
 
I've done some googling, and as usual found nothing but "may", "might", "perhaps". I copied and pasted the article below (but then couldn't find it again!) as an example (a) of scientists disagreeing, and (b) of some researchers favouring the theory that the expansion of the savannah forced early hominids to leave the trees and walk upright.-Did the first bipedal hominids live in the savannah or the forest?
 
Last year, a team of scientists announced that Ardi, a pre-human fossils dating back 4.4 million years ago, had lived in a wooded area, an idea that was revolutionary because it contradicted previous theories. However, according to new findings from another team of scientists who examined the exact same data, the environment of the first bipedal primates was more likely a savannah. -In 2009, a team from the University of California at Berkeley in the U.S. published in the journal Science data suggesting that the hominids of the species Ardipithecus ramidus, to which the Ardi fossil belongs, had lived in the woods of Africa. But recently another study published in the same magazine and based on the very same data contradicts this theory.-"Our team reviewed the data published by White and his colleagues last October [2009] and found that their data does not support this conclusion," said Naomi Levin, co-author of the new study, adding that the data indicated the opposite, that Ardipithecus ramidus lived in a savannah composed of mostly herbs and low-lying plants. -The environment in which these pre-humans lived is important to understand their evolution. The call of the savannah theory says that the expansion of this type of terrain was the reason these early hominids left the trees and began walking upright. The theory of life in a wooded setting, however, would require finding a new explanation for the developmental changes. -"If the habitat of Ardipithecus ramidus were savannahs where grass made up 60% of the biomass," says Levin, "we can not rule out the possibility that the open environment play an important role in human origins and, in particular, the origin of bipedal walking." He concludes: "Neither the public nor the scientific community should accept an exclusively forest habitat for Ardipithecus ramidus and the origin of bipedal walking because the data does not support it."-The authors of the research in 2009 have already responded in another article, defending the methodology and validity of their analysis and indicating that the area where the Ardipithecus ramidus lived was very diverse and that it is wrong to generalize about a single type of environment. -Would you still say that science leaves no room for the scenario I have put forward?