Question: why do we have a digstive system

Erin Pallott answered on 25 Mar 2025:

Great question!! Billions of years ago, our ancestors were made of single or just a few cells. They could get everything they need from the surrounding environment, like bacteria still do. As life evolved, it started to get more complex and do things single cells can’t. But as we get bigger, we need ways to make sure every cell and tissue has what it needs. Simple diffusion won’t be fast enough to reach the tissues in the centre of our body! So more complex life began evolving different tissues to do different jobs. The digestive tract is a way to pass contents from the outside world (food!) through our body where we can take what’s useful, but protect ourselves from the harmful. The circulatory system will then help pass that useful nutrition across our whole body to reach all the cells.