Anti-oxidants, uric acid, and evolution

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TL;DR Summary

Humans and higher apes don't break down uric acid. Why not? Was this 'de-evolved' and if so why?

This might be a 'that's just how it is' sort of question, but are there any theories of how humans and higher apes have evolved so that they don't break down uric acid?

All other animals break this down into allantoin, and fish go one further and break that down into ammonia.

Did 'us apes' end up 'de-evolving' this function, and if so is there any evolutionary benefit to having uric acid as an anti-oxidant present in our blood?

Presumably the ability to break down uric acid to allantoin came about after animals evolved to generate uric acid, so what's with the backward step for apes?

 

[TeethWhitener]

Wikipedia gives a couple of different theories along with links:
https://en.m.wikipedia.org/wiki/Uric_acid
https://www.nature.com/articles/228868a0
https://onlinelibrary.wiley.com/doi/abs/10.1046/j.1365-2362.1997.1390687.x
According to the articles, you seem to have answered your own question. Since higher primates lost the ability to synthesize ascorbate, another molecule was needed to act as a reducing agent in the body. A mutation that resulted in a loss of functional uricase would have served that function nicely and would therefore have been subjected to selection pressure.

 

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OK, I wasn't aware of the ascorbate-synthesis loss. So if that happened, then that could make sense.

So that was part of what I am interested in; what are the actual roles of anti-oxidants and how do they actually do their 'thing' that makes a difference? What I have read and heard sounds a bit 'hand wavy', TBH. What's the actual thing that they do and why does that help? As far as I understand it, for example, L-ascorbic acid can be both an anti-oxidant and pro-oxidant, depending on the chemistry, and at that point my non-chemistry engineering brain bogs over and I figure that's not something I'm going to get to understand with any degree of conclusive certainty.

 

[TeethWhitener]

Cellular respiration produces a lot of reactive oxygen species (ROS) as byproducts, but those species can do a lot of oxidative damage to other important molecules in the cell. Reducing agents (i.e., antioxidants) will react with these ROS and mitigate the damage that they cause. Again, wiki has a decent primer:
https://en.m.wikipedia.org/wiki/Reactive_oxygen_species

 

[jim mcnamara]

Explicit ascorbic acid example
https://www.intechopen.com/books/antioxidants/antioxidant-compounds-and-their-antioxidant-mechanism

Although @TeethWhitener answer is better.

 

[BillTre]

There are times in the life of some organisms when certain cells must die for the benefit of the whole organisms. This often done through programmed cell death. In these cases, reactive oxygen species are released to rapidly kill the cell. This usually occurs at mitochondria, where lots of reactive oxygen species are constantly being produced.

That your fingers and toes are not webbed, is the result of cell death in regions that would otherwise form the webbing.
Otherwise, you couldn't do this:

 

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There are times in the life of some organisms when certain cells must die for the benefit of the whole organisms...
Otherwise, you couldn't do this:
View attachment 285751

Grow pointy ears? :)

Thanks for the responses, I will look through these links.

 

[jedishrfu]

Thank you all for your great answers. Now it’s time to close this thread before we get inundated with Spockian humor.

Jedi