29 – Beginning of slow human growth and extended development
300,000 years ago
The human growth pattern is unique among all mammals on the planet, including our primate cousins. Compared to our closest living relatives, the chimpanzees, our offspring have a longer juvenile period as part of an overall growth timeline that is very prolonged. However, we know that by around 300,000 years ago, human growth first started following the same basic trajectory that it does today. We can study this growth rate through the patterns of tooth formation, in particular, by investigating a tooth’s hard, outer coating of enamel, which grows in increments, leaving growth lines, similar to rings within a tree. By studying the rate of growth from these enamel growth lines, scientists determined that around 300,000-year-old Homo sapiens individual had the same exact pattern of prolonged tooth development and eruption times as in modern human children.
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Epoch
Environmental and Climate Changes
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Earth’s climate remains relatively stable with alternating glacial and interglacial periods
Changing Species
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Homo erectus 1.8 Ma to 112,000 Ya
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Homo heidelbergensis 800,000 to 125,000 Ya
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Homo neanderthalensis arrives 400,000 to 30,000 Ya
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Homo naledi 335,000 to 236,000 Ya
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Homo sapiens 300,000 Ya to Present
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Homo neanderthalensis 200,000 to 28,000 Ya
