Are Humans Vegetarians or Carnivores?

Based on new research from researchers at Lund University in Sweden, eating meat is one reason behind the evolutionary success of humankind.  When our ancestors started eating meat and hunting, the new diet allowed women to wean their children earlier.  They could then have more children during their reproductive life which contributed to increased overall survival and population increases.

The research, which compared close to 70 mammalian species, found a clear connection between eating meat and a faster weaning process.  Experts agree that learning to hunt was a decisive step in human evolution.  Hunting requires communication, planning and the use of tools; all of which helped in the development of a larger brain.  Adding meat to the diet made it possible to develop this larger brain.

“This has been known for a long time. However, no one has previously shown the strong connection between meat eating and the duration of breast-feeding, which is a crucial piece of the puzzle in this context. Eating meat enabled the breast-feeding periods and thereby the time between births, to be shortened. This must have had a crucial impact on human evolution”, says Elia Psouni of Lund University.

The average duration of breast-feeding for humans is 2 years and 4 months which is short in relation to our maximum lifespan of around 120 years.  It is much less when compared female chimpanzees whose maximum lifespan is only 60 years yet suckle their young for 4-5 years.

Although many have tried to explain the shorter weaning period of humans based on social and behavioral theories, the Lund group has now shown that humans are no different than other mammals with respect to the timing of weaning.  It is brain development and diet composition which determine the time human young stop suckling.  This time period compares perfectly with the pattern in other mammals.

This model shows that the young of all species cease to suckle when their brains have reached a particular stage of development on the path from conception to full brain size.  Carnivores wean earlier than herbivores or omnivores and humans are most like carnivores with respect to timing of weaning.

In the past, researchers have often pondered the difference between humans and the great apes, which now seems to depend merely on the fact that as a species we became carnivores, whereas gorillas, orangutans and chimpanzees are herbivores or omnivores.

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