Evolutionary mystery solved: scientists have found out why our ancestors gave birth to twins 60 million years ago

60 million years ago, the birth of twins was common among primate ancestors. However, with the course of evolution, the number of offspring has decreased, and modern humans mostly give birth to only one child.

This conclusion was reached by anthropologists from Western Washington University and Yale University. The results of their research were published by Interesting Engineering.

According to the researchers, the transition of primates to predominantly monoecious reproduction coincided with the process of encephalization, an evolutionary increase in brain size. They note that over time, humans have experienced a decrease in the number of offspring in parallel with an increase in brain volume.

Researchers note that multiple pregnancies required significant energy and physical effort from the mother, making her life more difficult. Therefore, primates that gave birth to only one child had a better chance of survival.

Scientists Jack McBride and Tesla Monson emphasize that analyzing the number of offspring in mammalian phylogeny can provide valuable knowledge about evolutionary processes that have influenced the development of mankind.

The scientists used mathematical algorithms to map the number of offspring and study patterns. Since family fossils are very rare, they turned to public databases to collect anthropological data on pregnancy, as well as body size at birth and in adulthood.

The study found that multiple pregnancies in primates, including twins or even triplets, were associated with "smaller brain and body size, shorter gestation length, and faster growth."

Scientists also noted that the transition from multiple to single pregnancies in primates occurred several times. As a result, modern humans have larger brains and bodies, and usually give birth to only one child.

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