How did humans evolve from fish?

How did fish get legs and be able to breathe if they came out of water wouldn't they all die off before they can adapt like if humans were forced to stay under water we would die off before the time it took to adapt

1 Answer

Relevance
  • Anonymous
    8 years ago
    Favorite Answer

    it's a very gradual process (can take millions of years). There is variation among individuals in a population. In the case of fish living about 400 million years ago, there may have been some variation in fin shape. Some fish may have had thicker fins that allowed them to move onto muddy flats for short periods of time. Maybe there was food on these flats and no predators. This would have given them a selective advantage because they would have more access to food than their strictly aquatic kin, lived longer (possibly), and produced more offspring so that thick, fleshy fins became widespread in the population.

    The coelacanth is an extant fish that is considered a 'living fossil' -- it has thick, fleshy fins like those of ancestors of tetrapods.

    http://en.wikipedia.org/wiki/Coelacanth

    At the same time, it would have been even more advantageous for these fish to be able to breathe air. This is also a very gradual process. One theory is that gas bladders (keeps fish buoyant in the water) became vascularized and allowed for some exchange of oxygen gas with the blood. This wasn't very efficient, and these fish also had gills, but it gave them an advantage. There is a group of fish living today that can breathe air.

    http://en.wikipedia.org/wiki/Lungfish

    very neat stuff!

    edit: I forgot to mention Tiktaalik, one of the closer ancestors to tetrapods.

    http://evolution.berkeley.edu/evolibrary/article/e...

    http://en.wikipedia.org/wiki/Tiktaalik

Still have questions? Get your answers by asking now.