10 Reasons Why Humans May Not Have Come From Earth

In further expanding his argument, Silver points to the excessive nutrition on earth and a possible cause for the difficulties of human childbirth.

The fact that humans have to spend hours screaming in pain to bring new life into the world, whereas the rest of the animal kingdom can drop a sprog in their sleep, has long puzzled anthropologists. Why is it such an ordeal for us to have kiddies when it's literally our only biological purpose?

Silver thinks that the high levels of nutrition that we get could cause our babies to grow far bigger in utero than our bodies are designed to cope with. 

Indeed, it is a well-known phenomenon that people with diabetes have much larger than average babies due to the high sugar levels in their blood - this demonstrates that there is, in fact, a clear link between high nutrition and baby size. 

Whether or not that means that diabetics are even more alien-y aliens than us regular aliens, Dr. Silver doesn't specify.

Perhaps this is also a result of our newer, willowy frames (thanks to the lack of gravity, remember?). Perhaps, back on our own planet, there are a load of stocky, troll-like beings happily squeezing babies out of their wide, childbearing hips left, right and centre.