If the world was completely unchanging we wouldn't have to change to survive. As long as we
could live and reproduce in that world we and our children could always stay exactly as we were.
But our world is constantly changing.
And life forms are always finding ways to better eat us or compete against us for scarce resources.
So we have to change and adapt just to stay as successful as we were.
To change we need new DNA. We can make new DNA ourselves but, because we don't know how that
DNA code works, it's always just random mutations. We don't know whether the changes are going to be
good or whether the changes will work with the old DNA. It's always unexpected whether a gene
is going to be good or bad for us. Mutations are where new DNA comes from but we don't want
to rely on our own personal luck to get good new DNA because most of the time it's not good DNA.
We can try scavenging bits of code left over from dead cells.
At least we know it codes for something and one organism's trash could be our treasure. But,
of course if it came from something dead, it's not guaranteed to be useful.
So we want DNA from something that is still alive. This is the safest source for new DNA. Their life
is proof that it's probably good. But we still don't know if the combination of genes is good.
Maybe the new DNA is useful but it just doesn't work well with something we already have. The new
gene would be great but we have no way of getting rid of the old one that's holding us back
So maybe there's a better way. If we let go of the idea that we are one package
we can shuffle up our DNA and then combine it with someone else's. We still don't know what
combinations will work but, because our genes are getting split up, we get to test those
combinations. Our genes don't have to be tied down by one another and have more freedom to test their
potential. Our code will be repeatedly shuffled and tested against the gauntlet of life. The
best combinations will continue and the worst will die off. And that system continues to this day
But this shuffling comes at a cost. Any of our children of sex are only going to have half of
our DNA. So if we want to produce a full copy of ourselves we have to produce twice as many
children compared to asexual reproduction. So some creatures under good conditions will reproduce
asexually because it's easier to make copies. But they'll switch to sex when conditions are tough;
when change is necessary. Another cost of this shuffling if we can't reproduce on our
own we have to find a mate; we have to have structures and strategies for finding a mate.
Some insects spend over 50 percent of their total living energy budget just calling out.
But most of the time the benefit seems to be worth the cost. But if we are slow… very slow and or if
the population is very dispersed there can be a greater benefit in being hermaphroditic. If it's
hard to find a mate better if every member of your species that you run into is a potential suitor.
Also we can self-fertilize. But if we're born in the dark
finding a mate might be so rare that when we do we might be better off fusing our bodies
and staying together for the rest of our lives
But finding a mate is only a part of it. Everybody needs DNA to pair up with
so DNA becomes another scarce resource that we fight over.
We have to prove for the best we have to compete for love and sex.
So if our size is a big factor in these competitions we may benefit from switching
sexes. If there is a lot of male male competition we can't hope to win when we're young and small,
we could start life as a female where our size doesn't affect our reproductive success.
Then when we've grown enough to win these competitions switch to male.
Likewise if male male competition isn't that important but our ability as a mother
to hold more offspring or protect them is, we might be better off starting life as a male.
Then when we're big enough to hold and protect offspring switch to female.
These strategies and more help us to mix and match the sum of our best mutations.
To try to pass on the best parts of ourselves hooked up with the best parts of someone else's
to help us adapt to this forever changing place.