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> Biology is brutal and doesn't care about fairness or morality. I still try to meditate on the evolutionary advances for sexual vs asexual reproduction to beg

> Biology is brutal and doesn't care about fairness or morality. I still try to meditate on the evolutionary advances for sexual vs asexual reproduction to begin with. There's got to be a huge advantage of the separation of the sexes that is hard to fathom just because it's everywhere. Is it a springboard of genetic diversity that optimizes in ways we can't imagine otherwise? The 'compared to what' is always something I wanted to contemplate. Like why did organisms split into near copies of each other with male and female? Why had one developed that carried the womb and the other not? Was it just simple reproductive concurrency? The separation being the better evolutionary choice is so mysterious to me.

barrkel 6y ago
If you have advantageous mutations in two parallel family trees, sexual reproduction permits them to join into a single tree while asexual (splitting) doesn't. There's a similar effect for eliminating harmful mutations that coincide with beneficial mutations. It's more complex in practice for bacteria - there can be DNA transmitted horizontally - but bacteria usually win out by sheer numbers.
- Viliam1234 6y ago
  Another advantage is that a population that doesn't consist of clones is more resistant to diseases. With regards to "why separate sexes? why two?", the technical reason is mitochondria, the "cells" within our cells: you don't want the copies from one parent to fight with copies from another parent. The standard solution for the multicellular organisms is that only one parent provides mitochondria, the other does not. There were attempts with more than two sexes, turned out to be too complicated.
  - jxramos 6y ago
    Whoa, does this suggest something very sensitive, unstable, and delicate about mitochondria that their preservation must be highly conservative otherwise it could not be a steadily observed thing? How exactly would a fight ensue for the coding of a mitochondria? Are those organelles even created by ribosomes? How exactly are those things synthesized anyways?
    - Viliam1234 6y ago
      Unlike everything else in the cell, mitochondria are not created by the cell nucleus. They are semi-autonomous "cells in the cell". Like, that is their assumed evolutionary origin: a parasite that miraculously became a symbiont. The "outer cell" provides protection and food, the "inner cell" specializes on energy production. So what happens when a cell wants to become two is that the cell nucleus will (command to) synthesize another copy of all other stuff, but mitochondria just create their own copies by splitting in two. Now what would happen in sexual reproduction if each gamete would bring their own mitochondria? The "outer cell" would benefit from them living together peacefully, but if a mitochondrion would attack its competitors instead, it would be an evolutionary advantage. Even if it would reduce the probability of the whole cell surviving, as long as the chance of the cell surviving is greater than 50%, it is profitable for a mitochondrion to attack its competitors, because it will leave twice as many descendants if it wins. This would lead to arms race between mitochondria, and the cell would pay the costs. Except, there is this neat trick when the cell creates two types of gametes: those with mitochondria (i.e. female) and those without (i.e. male). Then there is no internal battle after joining. A few plants tried it with more than two sexes, where the rule was generally "any two individuals from different sexes can reproduce", and for each combination of sexes they knew which one provides the mitochondria and which does not. But most of nature settled on two sexes.
danielheath 6y ago
Without sexual reproduction, you are limited to cloning + random mutation at each generation to generate diversity. This generates fast-growing, homogeneous populations which get wiped out as a group when circumstances change to no longer favor them. Sexual reproduction lets you grab non-harmful mutations from another genetic lineage en masse at each and every generation. This means that when circumstances change you are far more likely to have at least one offspring which can adapt to the new situation. Because it can take hundreds of generations for helpful mutations to appear, and changing circumstances can wipe out an entire homotype, the advantages of preserving genetic diversity outweigh the costs.
- jxramos 6y ago
  aha, thank you. The compared to alternatives would be cloning, no change, or small and slow perturbations. Sexual reproduction === intentional mass mutations, that's such a clear way to conceive of it all. It's the genes that matter here at the end of the day. Wow
branko_d 6y ago
Evolution = variation + selection Variation = mutation + gene mixing (i.e. sexual reproduction) Without ability to mix genes, the species is left with only one kind of variation: mutation, which is horribly inefficient.

barrkel 6y ago

If you have advantageous mutations in two parallel family trees, sexual reproduction permits them to join into a single tree while asexual (splitting) doesn't. There's a similar effect for eliminating harmful mutations that coincide with beneficial mutations. It's more complex in practice for bacteria - there can be DNA transmitted horizontally - but bacteria usually win out by sheer numbers.

Viliam1234 6y ago
Another advantage is that a population that doesn't consist of clones is more resistant to diseases. With regards to "why separate sexes? why two?", the technical reason is mitochondria, the "cells" within our cells: you don't want the copies from one parent to fight with copies from another parent. The standard solution for the multicellular organisms is that only one parent provides mitochondria, the other does not. There were attempts with more than two sexes, turned out to be too complicated.
- jxramos 6y ago
  Whoa, does this suggest something very sensitive, unstable, and delicate about mitochondria that their preservation must be highly conservative otherwise it could not be a steadily observed thing? How exactly would a fight ensue for the coding of a mitochondria? Are those organelles even created by ribosomes? How exactly are those things synthesized anyways?
  - Viliam1234 6y ago
    Unlike everything else in the cell, mitochondria are not created by the cell nucleus. They are semi-autonomous "cells in the cell". Like, that is their assumed evolutionary origin: a parasite that miraculously became a symbiont. The "outer cell" provides protection and food, the "inner cell" specializes on energy production. So what happens when a cell wants to become two is that the cell nucleus will (command to) synthesize another copy of all other stuff, but mitochondria just create their own copies by splitting in two. Now what would happen in sexual reproduction if each gamete would bring their own mitochondria? The "outer cell" would benefit from them living together peacefully, but if a mitochondrion would attack its competitors instead, it would be an evolutionary advantage. Even if it would reduce the probability of the whole cell surviving, as long as the chance of the cell surviving is greater than 50%, it is profitable for a mitochondrion to attack its competitors, because it will leave twice as many descendants if it wins. This would lead to arms race between mitochondria, and the cell would pay the costs. Except, there is this neat trick when the cell creates two types of gametes: those with mitochondria (i.e. female) and those without (i.e. male). Then there is no internal battle after joining. A few plants tried it with more than two sexes, where the rule was generally "any two individuals from different sexes can reproduce", and for each combination of sexes they knew which one provides the mitochondria and which does not. But most of nature settled on two sexes.

danielheath 6y ago

Without sexual reproduction, you are limited to cloning + random mutation at each generation to generate diversity. This generates fast-growing, homogeneous populations which get wiped out as a group when circumstances change to no longer favor them. Sexual reproduction lets you grab non-harmful mutations from another genetic lineage en masse at each and every generation. This means that when circumstances change you are far more likely to have at least one offspring which can adapt to the new situation. Because it can take hundreds of generations for helpful mutations to appear, and changing circumstances can wipe out an entire homotype, the advantages of preserving genetic diversity outweigh the costs.

jxramos 6y ago
aha, thank you. The compared to alternatives would be cloning, no change, or small and slow perturbations. Sexual reproduction === intentional mass mutations, that's such a clear way to conceive of it all. It's the genes that matter here at the end of the day. Wow

branko_d 6y ago

Evolution = variation + selection Variation = mutation + gene mixing (i.e. sexual reproduction) Without ability to mix genes, the species is left with only one kind of variation: mutation, which is horribly inefficient.