Latest Research Says Modern Man Comes from Africa
By Jessica Berman
Washington
19 July 2007
The "out of Africa" theory holds that modern humans emerged from the continent some 50,000 years ago, replacing more primitive species including Neanderthals that existed on different continents.
The alternative theory, called the multiregional hypothesis, is that modern humans evolved from primitive species in many places around the world.
But in the 1990s, the multiregional hypothesis was largely discredited by the advent of genetic testing.
Still, biologist Andrea Manica of Cambridge University in England says there are anthropologists who believe in the multiregional theory.
She says that is because of differences in the appearance, or morphology, of primitive human skulls that have been uncovered on different continents.
"What we did, which I think really in a way brings the whole discussion slightly to a close, is actually to look at genetics and skull morphometrics at the same time with a single sort of framework," she explained. "And actually show that if you ask the question explicitly, 'Do we come from Africa?' Then the answer is yes no matter whether you look at genetics or whether you look at morphometrics."
Manica and colleagues measured 4,500 ancient human skulls from more than 100 populations around the world. She says the size and shape of the skulls were compared to those unearthed in Africa, which she says has a very diverse population.
"You find for example in terms of skulls, quite of a lot of variability on the traits," she added. "You know, how broad faces are and how narrow and deep, and so on."
The investigators discovered that the greater the distance from Africa, the less variability there was among the skulls.
"So, if you take skulls from a population in Africa, there is lots of variability," she noted. "If you go to Europe, there's a little bit less. If you go to Asia, it's going further down. If you go then to North America, it goes further down. And South America is really the most homogeneous in a way of [set] populations."
Manica says that the modern humans who left Africa were far less diverse than the human ancestors who remained behind. And those that traveled further afield were physically even less diverse, contributing to more physical uniformity on the continents where they settled.
The study of the origins of modern humans appears in the current issue of the journal Nature.
最新研究表明現(xiàn)代人來自非洲
“走出非洲”理論主張現(xiàn)代人類在5萬年以前出現(xiàn)在大陸,代替了更加原始的出現(xiàn)在不同大陸的人種尼安得特爾人。
選擇理論,稱為多地區(qū)起源假設,主張現(xiàn)代人類是由世界上很多地方的原始人種進化來的。
但是在1990年,在起源測試出現(xiàn)后,多地區(qū)起源假設大大失去了信譽。
盡管如此,英國劍橋大學的生物學家Andrea Manica 表示仍舊有人類學家相信多地區(qū)起源假設。
她說由于外表的不同,形態(tài)學解釋原始人類頭骨出現(xiàn)在不同的大陸。
“我們所做的和我們所想的確實在某種程度上可以引出相近的討論,實際上,遺傳構造和頭骨形態(tài)特征同時帶有單獨的某種構架。”她解釋道。確實如果你要明確地問這個問題,“我們來自非洲嗎?”無論你觀察遺傳構造還是形態(tài)特征,回答都是是的。
Manica和他的同事們觀測了世界上100多個民族的4500個原始人類頭蓋骨。她說頭蓋骨的大小和形狀與那些在非洲出土的相比較可得出人類種群豐富多彩。
“在頭蓋骨方面,你會發(fā)現(xiàn)特點有很多可變性,”她補充道。你可知道臉型有多寬,多窄和多深,等等。
調查人員發(fā)現(xiàn)距離非洲越遠,頭蓋骨變化性越小。
“所以,如果你取出非洲人的頭蓋骨,會發(fā)現(xiàn)有很多可變性。”她解釋道。“如果你去歐洲,變化便很小。如果你去亞洲,就會更小。如果你去北美,就會進一步小。在某種程度上來說南非的各種民族確實是同類的。
Manica表示離開非洲的現(xiàn)代人比留在后面的人類祖先具有很小變化。那些出行很遠的人身體上變化更小,他們在大陸上定居身體體型更加相似。
現(xiàn)代人類起源的研究來源于《自然》雜志的現(xiàn)期刊物。