Paleoanthropologists have wondered for a long time how and why humans evolved molars that emerge at these specific ages and why those ages are so delayed compared to living apes. New research solves this mystery.
Teeth are a really useful indicator of past environments. This is possible because teeth have biological rhythms and key events get locked inside them. These faithful internal clocks run night and day, year after year, and include daily growth lines and a marked line formed at birth.
As biologists explore the variation across the genomes of living people, they’ve found evidence of evolution at work. Particular variants of genes increase or decrease in populations through time. Sometimes this happens by chance. Other times these changes in frequency result from the gene’s helping or hindering individuals’ survival.