The confusion comes from the fact that several different events are being conflated. They are not all referring to the same thing.
Here's a rough timeline based on the current evidence:
- ~300,000 years ago: Homo sapiens first appears in Africa.
- ~195,000–130,000 years ago: There is evidence that human populations went through one or more severe bottlenecks, although their causes and severity are still debated. Some researchers link these to long periods of climatic stress, while others argue they resulted from a combination of factors. This is likely what Google AI was referring to.
- ~74,000 years ago: The eruption of the volcano at Lake Toba occurred. It was once thought to have nearly wiped out humanity, but that hypothesis is no longer widely accepted.
- ~70,000–60,000 years ago: Southern Africa experienced periods of severe drought associated with changing climate. Archaeological sites such as Pinnacle Point and Blombos Cave show that coastal populations survived by exploiting seafood, shellfish, and other marine resources. These populations also developed sophisticated stone tools and symbolic behavior.
- ~70,000–50,000 years ago: Modern humans began expanding out of Africa, eventually reaching Asia, Europe, and Australia.
- ~50,000 years ago: The Upper Paleolithic began in Europe. This date marks the appearance of advanced stone-tool industries there, not the end of an African drought. Humans had already been behaving in "Upper Paleolithic" ways in parts of Africa for tens of thousands of years.
The statement that "only about 7,000 humans survived" also needs some qualification. Older studies often estimated an effective breeding population of only a few thousand individuals. More recent genetic studies usually estimate an effective population size of roughly 1,000–10,000 breeding individuals, which does not mean there were only that many people alive. The actual census population may have been several times larger.
So the dates you've seen correspond to different ideas:
- 190,000 years ago: An early proposed population bottleneck.
- 70,000–60,000 years ago: A later period of climatic stress in southern Africa and the expansion of coastal populations.
- 50,000 years ago: The beginning of the Upper Paleolithic in Europe.
The version you previously read—that a drought reduced humans to a relatively small coastal population in southern Africa that later expanded—is still a plausible summary of one influential hypothesis. However, archaeologists today tend to view the story as more complex, with multiple climate fluctuations and population bottlenecks rather than a single catastrophic event that almost exterminated humanity.
