> Could it be that there was sexual reproduction first and asexual reproduction came later?

Unlikely. You can't mate with copies of yourself unless there are already multiple copies of yourself floating around.

I like the story they present in the article. For simple organisms, it's fairly inexpensive to let defective individuals die off. As organisms get more complex, it starts to become more costly to allow defects in the genetic code to persist. Then it becomes worthwhile to perform "integrity checks" to correct errors in the data as it's being copied.

If a population of organism is put into an environment conducive to a lot of data corruption, then the ones who are want to perform these checks are the ones who end up surviving.

You could imagine that when higher complexity organisms are exposed to high-stress environments, it would help establish their population's ability to sexually reproduce. The ones who aren't doing it will tend to die off.

Then as the complexity increases further, the genetic complexity itself can be a permanent endogenous source of high stress. The organism then loses the ability to produce asexually because it's no longer needed.

Sexual reproduction promotes genetic complexity because it allows us to survive while having more complicated genes. The recombination and mixing-and-matching only helps further the process along.

>Unlikely. You can't mate with copies of yourself unless there are already multiple copies of yourself floating around.

We don't know if early replicators were inside lipid membranes or not. If they were in the goop they'd be floating with their clones and siblings.

> Unlikely. You can't mate with copies of yourself unless there are already multiple copies of yourself floating around.

Asexual reproduction doesn't require copies of "yourself". Plants can self fertilize and they are some of the most complex organisms to do it and you probably know this.

Can you rephrase that statement?

I /think/ they're saying that if sexual reproduction came first, you have a pretty basic problem: where's the second individual that the first sexually reproducing entity mates with?

Sexual reproduction can involve an asexual (which would be hemaphroditic) partner.

Why would you evolve the necessary organs to sexually reproduce with your self, with no one else around?

Often times sexual organs are multipurpose. It's likely a genetic mutation that allows for sexual reproduction, as with all structural advances. I might end up with a functioning probiscus near my gamete sack and if I end up bumping into my fellow eukaryotes, that's just how it goes.

> is meiosis and mitosis the only two way to reproduce?

Well, from a high-level view the only way a cell can make more cells is to divide, and if it divides it either makes a copy of its genetic material first, or gives half of it to each daughter cell. So in that sense, they're the only two ways possible.

From a more detailed view, I wonder if the machinery of meiosis is evolutionarily the same in every sexually-reproducing species, or if it has evolved more than once. My guess is only once, because it has a specific sequence of events which is always the same.

>Well, from a high-level view the only way a cell can make more cells is to divide, and if it divides it either makes a copy of its genetic material first, or gives half of it to each daughter cell. So in that sense, they're the only two ways possible.

Ignoring the idea of three-way (or more) genetic swaps, which would be like another type of meiosis, what if there were other ways?

What if there was a "carbon copy" or "embossing" technique where a cell bumps it's genes up against other's genes, and through some process yet to be determined , the other's genes are "nudged" into conforming to the shape of the cell's bumping it?

Sort of like picking a lock.. you bump up against each cylinder enough times until it falls into the shape you want it to. No splitting of chromosomes, or transfer of actual genetic material needed.

Of course this is a pipe dream but I'm just imagining here.

Interesting thought. Theres no way for that to work with DNA really, since information is included there in a chemical sequence rather than a shape necessarily. Though there are epigenetic aspects that could maybe work that way, but that's not in the spirit of what you proposed. Maybe an alien form of life with a different information storage mechanism.

Right here at home though, if you want a life-approximating thing that actually does reproduce that way, you're in luck. Prions are proteins (a type of biological molecule) that make more of themselves in pretty much that way. They arent alive and they arent cells, but they reproduce by bumping into normally shaped proteins and making them be shaped in the same way. They cause all sorts of terrible diseases like mad cow and tend to be incurable since, well, theres really not much to kill or stop, it's just a protein, making other proteins look the same way, very fascinating and very scary - there are hypothesis that suggest prion like processes could be involved in neurodegenerative diseases like alzheimers.

https://en.wikipedia.org/wiki/Prion

Isn't that what we call a "virus"?

You might want to read upon horizontal gene transfer. But it's not reproduction.

Yes- this + mitosis of the new genetic code at sufficient scale would approximate a new form of reproduction.. there could be some organism that relies on it

The problem is you need two complete sets of reproductive organs simultaneously. If either the male or female has a single defective organ, nothing works.

Sexual reproduction is not about injecting a DNA (or RNA) into a host cell for one's own sake.

> Last question, is meiosis and mitosis the only two way to reproduce?

GP answer is a valid example?

Ok that sounds a bit pedantic. Reproduction is a technical term, sure. But its also a common term for life copying itself. But ok, sure.