https://genographic.nationalgeographic. ... n-journey/
最近十几年内,科学家从 Neanderthal 古代类人 (hominin or hominid) 遗留的骨头化石里提取了一些 DNA 样本,发现非洲之外的人类基本上都带有少量(2%左右)Neanderthal 的 DNA,说明在他们灭绝之前,即四万到五万年前, H. sapiens 和 H. neanderthalensis 曾有交配,很可能在非洲与欧亚大陆交界之处,即现代的中东地区。这个理论在几年前还非常有争议,但现在已经被科学界广泛接受,甚至 23andme 等基因分析网站已经纳入分析报告中。The earliest fossils of recognizably modern Homo sapiens appear in the fossil record at Omo Kibish in Ethiopia, around 200,000 years ago. Although earlier fossils may be found over the coming years, this is our best understanding of when and approximately where we originated.
According to the genetic and paleontological record, we only started to leave Africa between 60,000 and 70,000 years ago. What set this in motion is uncertain, but we think it has something to do with major climatic shifts that were happening around that time—a sudden cooling in the Earth’s climate driven by the onset of one of the worst parts of the last Ice Age.
Once the climate started to improve, after 70,000 years ago, we came back from this near-extinction event. The population expanded, and some intrepid explorers ventured beyond Africa.
Slightly later, a little after 50,000 years ago, a second group appears to have set out on an inland trek, leaving behind the certainties of life in the tropics to head out into the Middle East and southern Central Asia. From these base camps, they were poised to colonize the northern latitudes of Asia, Europe, and beyond.
人类迁徙还有另一条主要路线,从东非海岸航行到印度洋与太平洋,包括大洋洲诸岛,印度尼西亚,东南亚,印度南部,逐渐北上。最近的最近才有科学家怀疑,这一支人类与其他类人,尤其是 Denisovans 也有交换 DNA。Denisovans 是最近六七年才发现的古代类人,跟 Neanderthals 同时存在,但活动地区主要是亚洲,二者都比 H. sapiens 要早很多。详情见下面的报道:
http://news.nationalgeographic.com/news ... il-finger/
https://www.sciencedaily.com/releases/2 ... 133514.htm
虽然 Denisovans 的骨化石在中亚的阿尔泰山区发现,但 DNA 分析表明或许他们曾在亚洲活动非常广泛,跟人类交集时间大约是四万年前。可惜目前样本实在太少,不够跟现代人类的基因准确比较。目前测出亚洲和大洋洲人民带有一些 Denisovan DNA(目前估计1%以下),而且越往南成分越高。说不定过几年 23andme 又会加入每个人的 DNA 里的 Denisovan 成分分析。
然后问题就来了,Neanderthals, Denisovans, 还有其他几种古代类人(例如特别矮小的 H. floresiensis),在五到十万年前,曾跟人类同时存在且有直接的交集。考虑到这些类人的近似,可以推测他们也是智慧动物。然而在短短的几万年之后唯独剩下了我们,他们都灭绝了,只留下只言片语的 DNA。为什么呢?刘慈欣生怕人类被其他智慧生物给灭了,我看是其他智慧生物碰见人类要躲远点还差不多。