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Asked by to Anna, Chris, Jane, Iain, Nick on 18 Mar 2014. This question was also asked by .
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Anna Middleton answered on 18 Mar 2014:
Hi kaylaahbieberr
We are 70% water because this is the way that we have evolved to be the best that we can in our current environment.
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Iain Moal answered on 18 Mar 2014:
This is a really good question, and Anna is right, it is because of our evolution. Early life arose in the water, and all of the most basic biological processes that evolved were ones that took place in water. So, when our fish ancestors moved onto the land and evolved into reptiles and amphibians, instead of having to change all of their fundamental biochemistry to fit a dry environment, which would be basically impossible, they instead carried all the water they needed inside of them. This is also the reason why blood is salty, because biochemistry evolved in salty sea water.
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Jane Charlesworth answered on 18 Mar 2014:
Good question! Our bodies are made up of millions and millions of tiny cells, which are like little balloons filled with a mixture of water and chemicals and structures that our bodies need to function. When we drink water, it goes into the space between our cells and from there into our cells.
We use up water in our body processes like digestion, breathing (this is why your breath steams up on a window–you breathe out some water vapour) and weeing and so we need to put more water back in, to keep our bodies at the right level.
The reason our cells contain watery goo is because the very first life on Earth was a single cell and more complicated bodies, like ours, evolved from that simple structure.
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