Why do animals only breed during specific seasons, but human don’t?
In: Biology
Most animals breed timed so that the young emerge during times of high seasonal food availability. For example, migratory birds lay eggs as soon as possible in their usual habitat so that the young have a long warm season with ample food so they can be big enough to make the winter migration.
Long before homo sapiens evolved, our primate ancestors managed to be successful enough to provide for their young even in dry or cold seasons. So the need for timed births was greatly reduced.
But at the same time early primates were mastering their environment, their brains were getting bigger, forcing mothers to deliver earlier so that the baby’s skull could still fit through the bipedal pelvis. Primate babies are born weak and helpless and needing to grow and learn a LOT compared to four legged animals. (Deer, horses and cows can walk and eat within an hour or so of birth) This meant that raising young primates take more time and resources.
The best way early primate females had to increase their access to resources was to be sexually available all the time. Using sex as a lure, she gave males a good reason to stick around and provide food and defence. As part of this, females evolved to hide their fertile periods to some extent. So a male who wanted to sire her children had to stick around even when there were no young at the moment. Along the way, fertile periods went from seasonal to monthly.
Latest Answers