Humans have gone through many major developmental stages since distant relatives diverged from gorillas and chimps. This divergence is believed to have begun 6-10 million years ago; it was not a simple overnight process. Approximately 4 million years ago one significant change occurred when our ancestors began to walk upright. This allowed them more use of their arms and hands. 3 million years ago the species divided into two, possibly three hominid species. These two types of man evolved differently. Only one survived. About 2.5 million years ago man began to use crude tools, stones and wood. Anatomically we resemble man from about 60,000 years ago but behaviorally we are very different. Diamond states that in the region of 35,000 years ago man began to evolve intellectually with the use of simple language.
Diamond stresses the anatomical difference between Neanderthal man and modern man. He describes Neanderthal man as having very distinctive facial features: "eyebrows resting on prominently bony ridges", the eyes were set deep in the eye sockets, while the nose and jaw protruded out. The lower jaw sloped backwards as they had no chin. Unlike our vertical foreheads, Neanderthal mans sloped backwards. Neanderthal man had a brain that was about 10 percent larger than ours but obviously did not use it in the same way as we do. They were of a shorter, stockier build but were very muscular and strong. Their bone structure was also a great deal denser than ours. Diamond also offers the possibility that the gestation period for Neanderthal woman was 12 months rather than our 9 months. The life span of the Neanderthal was much shorter than ours, 30 to 40 years. In similarity to us the Neanderthals buried their dead, used fire on a daily basis and the greatest similarity is that they cared for their sick and elderly.
It is possible that Cro-Magnon replaced Neanderthal many surviving the ice-age. Another possibility is that by entering into areas inhabited by Neanderthals, the Cro-Magnons inflicted them with diseases that Neanderthal man was not able to resist.
