The adaptations we don't need (opens in new tab)

Despite human embryos gaining all their nutrition from the mother and from the mother's blood via the placenta, there still exists a yolk sac which is attached via a very slender tube to the gut\. The yolk sac is entirely empty of anything useful, says Alice Roberts, so why is it still there? Maybe it's too difficult to write it out of the of the genome\. Or maybe actually it does do useful things\. Whatever the case, it shows us we once had ancestors that laid eggs\. Tap link in bio to watch...