What was it that caused our ancestors to go from the tree tops to the ground?

Question

I understand that once the trees in Africa started to diminish, our ancestors (Australopithicus afarensis, africanus, etc.) had to learn how to walk upright on the ground or natural selection would not favor them. But what caused the trees to diminish? A drought obviously... but what caused that? I heard that it was caused by the Himalayas, but that just doesn't sound right to me.

Christians: I'm begging you, PLEASE DON'T ANSWER WITH ANY SORT OF BIBLICAL REFERENCES OR VULGARITY AGAINST EVOLUTINO!!! PLEASE!?!?!?!? It's a damn shame that I have to ask Christians not to be rude.

Answer 1

Gravity.

Answer 2

Do not blame it on Himalayas. Himalayan Mountain range formed, because of Continental drift. This is only a geographical change, and nothing to do with, evolution.

Yes, our ancestors were living on trees, only because, their food was available on trees. Further with the fear of predators, living in ground at that time, they were spending most of their time on trees. Gradually, they picked up the courage and started wandering in land also.

Further, evolution to Humans, was not confined to Africa only, it was happening, all over the Globe.

Charles Darwin, presented his theory of evolution in 1859, after lot of controversies, they theory is now accepted Universally. The concept later enlarged by the growth of Science of Genetics, based on Mendel's laws of inheritance, and extended through the work of T.H.Morgan, H.J.Muller and others.

What caused the, complete vanish of Dinosaurs ? same might have caused the loss of vegetation in Africa. A meteor hit, resulting in Snow age ? Various theories, different to each School of thought. Unless proven, how can you and me conclude.

But gradual, arrival of our ancestors from trees to land, learning to stand, hence the arms became short, tails vanished... etc., are all well known facts. And accepted by present day Homo sapience, ( phitecantropus erectus ).

What has happened during evolution is already happened, we Humans have adopted to it. Let us leave, all questions to the Scientists in that Field, let us live in harmony, with out targeting any religious groups.

Answer 3

I think that this makes the fundamental assumption that our common ancestor was tree-dwelling. I could be wrong but I've not read anything to support that.
If it is true, though, a great deal of social evolution has been attributed to the move to the ground, and that move has been studied in Bonobos v. Chimps. In their case I believe it was due to the location of their food supply, which is correlated with climate. Climate is always a good bet. ;)

Answer 4

The end of the Ice Age caused massive floods which were followed a chaotic spell of weather. A long dry period ensued which wiped off the great forests of the Sahara. It turned into a Savannah which was not the ideal place for lumbering apes especially with sabre tooth tigers around.

Answer 5

LOL @ curious :)

Since I found that so hysterical, it's definitely time to go to sleep. Sorry this wasn't a real answer... I'll star to make up for it.

Answer 6

What is evolutino? Are you dissing hispanics?

Answer 7

Maybe they were having trouble fornicating on the limbs, or wanted to try more positions. But also the Ice Age might have played a fundamental role. Hold on, let me see what Wikipedia reckons:

The evolutionary history of the primates can be traced back for some 60 million years, as one of the oldest of all surviving placental mammal groups. Most paleontologists consider that primates share a common ancestor with the bats, another extremely ancient lineage, and that this ancestor probably lived during the late Cretaceous together with the last dinosaurs. The oldest known primates come from North America, but they were widespread in Eurasia and Africa as well, during the tropical conditions of the Paleocene and Eocene.

With the beginning of modern climates, marked by the formation of the first Antarctic ice in the early Oligocene around 40 million years ago, primates went extinct everywhere but Africa and southern Asia. Fossil evidence found in Germany 20 years ago (Begun, Journal of Human Evolution, 2001) was determined to be about 16.5 million years old, some 1.5 million years older than similar species from East Africa. It suggests that the great ape and human lineage first appeared in Eurasia and not Africa.

The discoveries suggest that the early ancestors of the hominids (the family of great apes and humans) migrated to Eurasia from Africa about 17 million years ago, just before these two continents were cut off from each other by an expansion of the Mediterranean Sea. Begun says that the great apes flourished in Eurasia and that their lineage leading to the African apes and humans—Dryopithecus—migrated south from Europe or Western Asia into Africa. The surviving tropical population, which is seen most completely in the upper Eocene and lowermost Oligocene fossil beds of the Fayum depression southwest of Cairo, gave rise to all living primates—lemurs of Madagascar, lorises of Southeast Asia, galagos or "bush babies" of Africa, and the anthropoids; platyrrhines or New World monkeys, and catarrhines or Old World monkeys and the great apes and humans.

The earliest known catarrhine is Kamoyapithecus from uppermost Oligocene at Eragaleit in the northern Kenya rift valley, dated to 24 Ma (millions of years before present). Its ancestry is generally thought to be close to such genera as Aegyptopithecus, Propliopithecus, and Parapithecus from the Fayum, at around 35 Mya. There are no fossils from the intervening 11 million years. No near ancestor to South American platyrrhines, whose fossil record begins at around 30 Mya, can be identified among the North African fossil species, and possibly lies in other forms that lived in West Africa that were caught up in the still-mysterious transatlantic sweepstakes that sent primates, rodents, boa constrictors, and cichlid fishes from Africa to South America sometime in the Oligocene.

In the early Miocene, after 22 Mya, many kinds of arboreally adapted primitive catarrhines from East Africa suggest a long history of prior diversification. Because the fossils at 20 Mya include fragments attributed to Victoriapithecus, the earliest cercopithecoid, the other forms are (by default) grouped as hominoids, without clear evidence as to which are closest to living apes and humans. Among the presently recognized genera in this group, which ranges up to 13 Mya, we find Proconsul (genus)proconsul, Rangwapithecus, Dendropithecus, Limnopithecus, Nacholapithecus, Equatorius, Nyanzapithecus, Afropithecus, Heliopithecus, and Kenyapithecus, all from East Africa. The presence of other generalized non-cercopithecids of middle Miocene age from sites far distant—Otavipithecus from cave deposits in Namibia, and Pieroloapithecus and Dryopithecus from France, Spain and Austria—is evidence of a wide diversity of forms across Africa and the Mediterranean basin during the relatively warm and equable climatic regimes of the early and middle Miocene.

The youngest of the Miocene hominoids, Oreopithecus, is from 9 Mya coal beds in Italy.

"Modern humans are actually hybrids created by millennia of interbreeding between early hominids and chimpanzees," according to geneticist James Mallet and other MIT and Harvard scientists, as quoted in the newsmagazine This Week, June 9, 2006. The interbreeding began about 6.3 million years ago. Then, for a million years, the ancestors of the human race "continued to acquire chromosomes from chimps until a second and final break about 5.3 million years ago."

Molecular evidence indicates that the lineage of gibbons (family Hylobatidae) became distinct between 18 and 12 Ma, and that of orangutans (subfamily Ponginae) at about 12 Ma; we have no fossils that clearly document the ancestry of gibbons, which may have originated in a so far unknown South East Asian hominid population, but fossil proto-orangutans may be represented by Ramapithecus from India and Griphopithecus from Turkey, dated to around 10 Ma.

Molecular evidence further suggests that between 8 and 4 Mya, first the gorillas, and then the chimpanzee (genus Pan) split off from the line leading to the humans; human DNA is 98.4 percent identical to the DNA of chimpanzees. We have no fossil record, however, of either group of African great apes, possibly because bones do not fossilize in rain forest environments.

Hominines, however, seem to have been one of the mammal groups (as well as antelopes, hyenas, dogs, pigs, elephants, and horses) that adapted to the open grasslands as soon as this biome appeared, due to increasingly seasonal climates, about 8 Mya, and their fossils are relatively well known. The earliest are Sahelanthropus tchadensis (7–6 MYA) and Orrorin tugenensis (6 MYA), followed by:

Ardipithecus (5.5–4.4 MYA), with species Ar. kadabba and Ar. ramidus;
Australopithecus (4–2 MYA), with species Au. anamensis, Au. afarensis, Au. africanus, Au. bahrelghazali, and Au. garhi;
Paranthropus (3–1.2 MYA), with species P. aethiopicus, P. boisei, and P. robustus;
Homo (2 MYA–present).

Yeah! Thought so!