
Learning about evolution from species who thrive without sexual reproduction - pmcpinto
http://nautil.us/issue/42/fakes/when-pseudosex-is-better-than-the-real-thing
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forgotpwtomain
Interesting comment in the article's native discussion:

> Chris Jankowski • 2 hours ago

> The author says that sex "imposes a huge cost on a species, and that cost is
> called “males.”" Well, if the males are such a cost to a species, then why
> nature does not respond by heavily skewing the sex ratio of the offspring
> towards females. Males produce sperm which is cheap compared with the cost
> of producing eggs. A male could fertilize eggs of many - tens or hundreds of
> females. So the ratio could be 1 to 10 or even 1 to 100. But I do not know
> of a species that would do this.

> Some marsupials - possums and kangaroos create some skew, but is is slight
> and in response to environmental conditions or is more sequencing oriented
> depending on the age of the breeding female.

~~~
chongli
The answer to the first question is Fisher's Principle [0]:

 _Suppose male births are less common than female.

A newborn male then has better mating prospects than a newborn female, and
therefore can expect to have more offspring.

Therefore parents genetically disposed to produce males tend to have more than
average numbers of grandchildren born to them.

Therefore the genes for male-producing tendencies spread, and male births
become more common.

As the 1:1 sex ratio is approached, the advantage associated with producing
males dies away.

The same reasoning holds if females are substituted for males throughout.
Therefore 1:1 is the equilibrium ratio._

[0]
[https://en.wikipedia.org/wiki/Fisher%27s_principle](https://en.wikipedia.org/wiki/Fisher%27s_principle)

~~~
cousin_it
That's not really an answer though. Females could choose to reproduce
asexually. Even some large animals can still do it, like sharks. The mystery
is why they don't do it all the time. What's the genetic benefit of making
daughters that need males to reproduce, instead of making daughters that can
clone themselves? Handwaving about "introducing variation via sex" doesn't
help, because bacteria are the fastest evolving critters around and they
reproduce asexually.

~~~
reubenswartz
Bacterial genomes are much, much simpler than animal genomes. They reproduce
very quickly, and even if many bacteria suffer from a problematic (or fatal)
mutation, others will be OK, and some may even have adaptations to changing
conditions.

Animals have much more complex genomes. They are more at risk from mutations,
and they cannot reproduce as quickly. There is more incentive to "get it
right", if you will. With asexual reproduction, selection occurs at the level
of the genome, meaning you are as good as your "worst" gene. You can't get rid
of harmful mutations, and it seems like (complex) species that get stuck in
asexual reproduction go extinct.

With sexual reproduction, selection can occur at the level of the gene,
allowing beneficial mutations or recombinations to spread through a population
AND correcting (many) harmful mutations.

~~~
spacehacker
The dropout regularization method for neural networks was sort of inspired by
this observation, i.e. that recombination (combining genes of more than one
individual) makes the resulting structures more robust [1]. The idea is
basically that it avoids overfitting to the evolutionary context. This has two
effects: the fitness cannot change very quickly in response to single
mutations, and, conversely, it avoids that genes co-adapt such that the entire
genome becomes inflexible at exploring alternatives.

To achieve the same without sex, mutations would would have both break up the
co-adapted genes without breaking their functions and also find a good
alternative mutation. With sex, it does not matter if co-adapted genes are
broken up, because they are forced to evolve to deal with it. (This is kind of
similar to the concept of _learning to learn_ in neural network research.)
Also, if a parent gene is unfit, it is possible that the child can escape this
mutation by receiving that part of the genome from the other parent instead by
a 50% chance.

[1] [https://arxiv.org/abs/1207.0580](https://arxiv.org/abs/1207.0580)

------
zer0gravity
This is very interesting. This particular whiptail lizard carries 3 sets of
DNA, instead of the regular 2 that the sexually reproducing species have.

This seems to be a hybrid species that resulted from the sexual reproduction
of two different species many thousands years ago.

From the 3 sets of DNA, 2 are from the ancestral mother and 1 from the
ancestral father, and using this trick, each generation manages to keep the
whole DNA information of the original two without loosing it, like it happens
in the sexual reproduction, and also provide enough genetic variation in
newborns to allow evolution.

So I would say that basically, each individual is the child of that ancestral
pair that generated this lineage.

------
bitwize
I'm reminded of the asari, an all-female race of aliens from Mass Effect. They
reproduce asexually and so don't actually have sex, but there's a thing they
do called "embracing eternity" that's very pleasurable for both partners and
somehow lets the asari introduce genetic variation into their offspring.

(They also _look_ very sexy -- to several different species -- allowing them a
wide pool of partners to "embrace eternity" with.)

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akkartik
Reading this article, I had a minor epiphany: Sex is just really _really_
sophisticated ASLR.

[https://en.wikipedia.org/wiki/Address_space_layout_randomiza...](https://en.wikipedia.org/wiki/Address_space_layout_randomization)

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jotadambalakiri
I don't understand what nautil.us tries to be, it seems neither more
interesting nor more scientific than the science/tech column of any major
newspaper.

~~~
pessimizer
It started off more interesting and more scientific, but once it had
established the brand, it quickly had a reversion to the mean. Shitty content
will always be cheaper to find and produce; hyperbole and specious
associations will always attract more clicks. The magazine business is tough.

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kod
That article title is unfortunate, because it's actually the most interesting
thing I've read all week.

~~~
Maken
The title is pure clickbait that has little to no relation with the actual
content.

~~~
forgotpwtomain
It's not 'pure' clickbait if you read down to the part about the whiptail
lizard's being able to take on either sexual role which stimulates
reproduction but that's a rather minor detail. Also it's not at all supported
that unisex whiptail lizard's are better off than normal sexually reproducing
lizards.

In general I tend to agree title is not well fitted and the subtitle does
better:

> What we can learn about evolution from species who thrive without sexual
> reproduction.

One can only speculate that their editor came from a publication with a habit
of writing clickbait titles.

