Question 1: Was there a time when all humans spoke the same language?
From what we know (or can infer) about the social life of early humans in the Middle Paleolithic period (300-30 thousand years ago), our hunter-gatherer ancestors lived in small nomadic bands, each consisting of a few dozen (20-50) individuals. Several such bands may have maintained regular contacts and converged into loose ethnic units (“tribes”) totalling a few hundred members, which gathered seasonally for collective purposes such as ritual celebrations, marital exchange, etc. In such conditions a single speech community, capable of maintaining a shared linguistic code (unified by cultural transmission), can hardly grow larger than a tribe. In effect, a cluster of allied bands corresponds to a linguistic unit as well as a cultural one (with a shared system of customs and laws). Such a model is supported by studies of modern societies retaining an archaic type of organisation, such as the Indigenous Australians. At the time of first European contact, the population od Australia was probably about 300-500 thousand (its exact size is a matter of debate, but most estimates range within those limits). It supported about 250 tribal groups, each with its own language (sometimes more than one). Many of those languages were further subdivided into fairly diverse dialects. While some languages could boast one or two thousand speakers, others had just a few hundred (alas, those that have survived till now too often have only a few). It seems reasonable to assume that the speech communities of Paleolithic hunter-gatherers did not normally exceed about 1000 members.
In order for a single language to spread over the whole human population, that population would have had to be sufficiently small and geographically restricted. Population genetics can estimate past population sizes by reconstructing the family trees of a sample of DNA sequences found in the modern population. Roughly speaking, a population bottleneck at some time in the past narrows down genetic variation and reduces the number of ancestral lineages, as if forcing the genealogies of the modern variants of numerous DNA segments to coalesce within the same period. One recent study (Li &Durbin 2011) uses coalescent simulation applied to the complete human genome to show that the so-called effective population size (Nₑ) of non-African humans seems to have dropped down to about 1200 at some time 10-60 thousand years ago. The African effective population was also reduced, though less severely, to about 5,700. Does it mean that the global population of humans was less than 10,000?
|Humans were here. Many humans.|
Source: Wikimedia Commons
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