Eli5: We have a dna correction system to avoid variations, but, sexual reproduction to promote variations. So, Are variations good?
In: Biology
Lets explain it with cars!
A random change in DNA does a single tiny thing which still could have vast consequences:
A different color. A missing screw (is it crucial?). An extra screw fixing that annoying wobble. And 5 tiny screws that do absolutely nothing. Maybe only 3 tires. 5? How about rectangular ones! An extra seat on the top… or on the bottom.
Some of those are pretty bad. Many are mostly inconsequential, slightly annoying at worst. And some few might turn out to be actually helpful. That’s **genetic mutations**, random undirected changes to see what works out and what not.
**Sexual reproduction** is then taking two old cars, taking parts from both, and make a new one with them. Cars tend to have 4 tires, so the child will, too. Only one steering wheel, right? Seats… there’s some variance here. And the color is pretty much a matter of preference. We aren’t inherently changing the individual parts, we only copy them from earlier models.
If we design a new car, we might want to take those “parents” that worked particularly well. Maybe we liked one color more. And the idea of putting the steering wheel _on the left_ was really just better. Oh and please don’t use that fifth wheel idea anymore.
The decision what is kept in the next generation is mostly decided by two aspects:
– **Survival**: did it survive long enough?
– **Sexual selection**: Did they like it?
The safest car won’t sell if it is really uncomfortable or expensive. Nor will a car that is known to be a death trap. And people probably laugh about a seat on top. Without the second part, sexual selection, we mostly measure if it can drive well enough to not immediately crash; but with sexual reproduction, there’s now a lot of new secondary factors.
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