Theory that all men were white agree or disagree?

Question

We have come to learn that through evolutionary theory, a stimulus is introduced to our enviroment and we develope an advantage. Somehow the human body developed pigmentation az a means of defense so anyone south of the equator had alot of pigmantation while northern animals had less? agree or disagree and why?

I Figured because there was a super continent pangea that there would be one singular stimulus some of the ideas here have been mentally stimulating and I never thought that a permanent pigmentation black would be the origin and that the further north the stimulus weakens.. Its Mind boggling, however, I see not how dark skin is an adaptation from prior predecessors? And if so there had to have been albino traits until extreme exposure led to pigmantation development as a means to provide daily protection from free radical damage to cells?

Answer 1

It gets colder and less sunny south of the equator, and colder and less sunny north of the equator. The equator is the hottest and sunniest region. Maybe you meant "south of the Tropic of Cancer":
http://upload.wikimedia.org/wikipedia/commons/1/1c/World_map_with_tropic_of_cancer.jpg

Consider, however, that humans came from Africa, where strong sunlight tends to give light-skinned individuals cancer. It is quite obvious that humans were all dark-skinned initially. Only after moving far north did humans encounter regions with so little sunlight that rickets (from lack of vitamin D) became a greater threat than skin cancer. It is in this region that humans evolved light skin to allow greater production of vitamin D.

Answer 2

I disagree with your caption, though I think what you are trying to say could be more or less correct. Darker pigmentation helps to defend against UV rays.

That is not to say that all men were white. In fact, it would probably have been the exact opposite, as current theory holds that humans came out of Africa, in two waves. The ancestors of the Australian aboriginies were first. They of course have dark skins. According to the classic version of the theory, the ancestors of Europeans, Asians, Middle Easteners and Native Americans came in the second wave. Among them some have darker skins, and some have lighter skins, and there is a tendency toward darker skins nearer to the equator.

Your phrase "south of the equator" should rather read "near the equator". There is more sun near the equator than further away, not more sun south of the equator. Most of Africa, as indeed most of the populated world, is north of the equator.

It is possible that skin colour could have switched several times in the ancestry of an individual.

Answer 3

Disagree.

Human evolution is still hotly-debated and the fossil record is patchy.
However, we can be fairly sure humanity evolved in Africa from ape-like ancestors, and apes generally have skin pigmentation.

So, the first proto-humans would have had melanic skin. When the first diaspora of humanity occurred, some of those peoples *lost* their skin pigmentation; this is an advantagous trait in more northerly latitudes, because it helps with the production of Vitamin D from sunlight, and the risk of UV damage to skin is less at more extreme latitudes, so it was selected for and became the predominant trait.

Answer 4

the theory behind your idea is right.
your assumption (that humans were originally white) is wrong.


it is the LOSS of pigment which humans developed, i.e from black to white. dont you know that we all come from africa?

the loss of pigment is supposed to be an adaption to cooler and darker environments, because vitamin D is made in the body when it receives sunlight.

in fact, the further north you go (in europe at least), the paler, and blonder people get