Method to share genetics beyond traditional sexual reproduction

Question

It seems that my ability to create interesting creatures is limited by the need for sexual reproduction, which is absurdly useful, but also rather limiting, method of sharing genetics. I acknowledge that any sapient species will almost certainly have some means of swapping genetics, but that does not mean a traditional male-female role must exist.

I'm looking for some alternate approaches with which an 'advanced' species, at least sentient if not sapient, could evolve for exchanging genetics. I'm looking for any novel approaches for genetic swapping which make logical evolutionary sense. Presume a world that is roughly similar to earth, though your welcome to tweak specifics to fit any need. Any creature must be roughly earth like, meaning carbon based, multi cellular, specialized organs, etc etc. I'll give some lead way for methods of genetic encoding beyond DNA if this supports an interesting concept.

Genetic division does not need to be as rapid as with sexual reproduction, a species that gets enough novel DNA to make evolution of more advanced features like sapience possible is fine, even if it takes five times the generations due to a slower dna exchange mechanism.

What I mean by avoiding sex means avoiding the traditional male-female sexes or traditional "two creatures meet up and mate with intent of creating at least one more creature with half their dna each". It's okay to have specialized sexual organs, transfer of dna between creatures etc, so long as it is separate enough from traditional matings within the animal kingdom.

As I myself already stated I don't considered tri-gendered creatures to be viable (How to handle a tri-gendered race). Hermaphrodite creatures are interesting and novel, but I'm going to exclude them as possible answers simply because I'm aware of them and the interesting options they offer already.

What other novel methods could organisms generate to allow genetic exchange?

Answer 1

The simplest solution IMHO would be a symbiotic bacteria that is not trapped inside the cells, but instead lives at least partially outside the host cells and can be transferred between hosts.

Some bacteria in our digestive system actually are like this and their health and genetics does have an effect on the health of the host. Some larger parasites are potentially also very close.

Essentially you want a small species with fast life cycle living inside the host in a symbiotic relationship that can spread from host to host. Such species can potentially have arbitrarily large influence on the host, some insects can't reproduce without their parasites. And many parasites do affect the brain.

Not sure if this would necessarily speed up evolution, but it would create an alternate method of genetic transfer between hosts. Which is what you wanted. It is normal for genetic material to get transferred between host and parasites even.

For faster evolution, you need greater evolutionary pressure. There should be clear benefits for being the smartest guy around. Not sure if that is realistic. Thinking is fairly energy intensive. And after a certain point societies form and social evolution becomes the dominant factor.

Answer 2

What I mean by avoiding sex means avoiding the traditional male-female sexes or traditional "two creatures meet up and mate with intent of creating at least one more creature with half their dna each". It's okay to have specialized sexual organs, transfer of dna between creatures etc, so long as it is separate enough from traditional matings within the animal kingdom.

I think this condition holds the key to the answer. While there is an evolutionary need to mix DNA in reproduction (and thus, for specialized organs, which are sexual by definition), using half the DNA of two organisms is a bit arbitrary. (It's arguably the simplest solution, but definitely not the only one.)

I propose a race of unisexual creatures. Every member of the race has two reproductive organs; let's call them a "giver" and a "receiver". When two organisms have sex, the giver deposits some of its DNA into the receiver (much less than half; say 1 - 5%). The receiver doesn't contribute any DNA; rather, it "compiles" the DNA of numerous partners until it has a full set of chromosomes from which to create an offspring. At this point, pregnancy and childbirth occur and more or less resemble those of humans.

A species evolving this way would suggest an early threat to their survival that required more genetic diversification than the male-female method would have provided, such as a predator or virus that adapted to specific gene sequences. I also suspect that early in their evolution, each organism's giver secreted a random combination of genes, but as they evolved, they began secreting only their best genes, and secrete very similar genetic code every time. This would in turn drive the need for many mates, rather than mating with one organism (or yourself) many times.

Should you use this idea, I hope you enjoy exploring how this biology would affect their attitudes on sex and relationships.

EDIT (In response to your comment):

For what it's worth, I don't think common DNA is the only factor that motivates a parent to raise a child. Further, if the evolution I proposed did occur because of a survival necessity, there would be a reason for the organism to also evolve in a way that ensured a maternal instinct. There are several ways this could occur. Perhaps when one is pregnant, the body produces a specific hormone that stimulates the maternal instinct. Perhaps the mother contributes as small an amount of DNA as the fathers (or smaller), but the mother's DNA is always a specific gene sequence that is uniquely valued and/or responsible for how the organisms identify one another (e.g. a particular scent).

Later in their evolution (and as their society develops), they will also be motivated by the knowledge that they "designed" their offspring by selecting the mates, as well as by the social contract stipulating that they must nurture their own offspring so that in return others (whose offspring carry their DNA) will do the same.

And of course, there is the evolutionary imperative that one's species survive, as well as one's specific DNA. It stands to reason that this drive would be stronger in a species where offspring possess little or none of their parent's DNA.

Answer 3

There are many organisms on earth that have decoupled genetic recombination and reproduction. What you are looking for is called Horizontal Gene Transfer. This is when two organisms exchange DNA and there are lots of different ways it can happen. Many organisms have dedicated systems for exchanging genetic material, like a pilus for bacterial conjugation, but it can also happen through viruses, and even simply by accident. Many cells will add foreign pieces of DNA to their genome if it gets in to their nucleus. These systems are seen mostly in unicellular organisms, but there are multicellular examples and there is no fundamental reason why multicellular organisms can't utilize horizontal gene transfer. In fact some researchers believe from even humans contain some genes that we acquired through horizontal gene transfer. (In case there there is a paywall to that journal here is a news article about it).

In the end DNA, or any other genetic material, is just a physical molecule. An organism can make as many copies as it wants, translate it into different forms, and spew it all over the place. It's very easy to imagine an organism that makes copies of some or all of its DNA and simply shares them with other members of its species through any sort of direct or indirect physical contact. Just to give an example, imagine an alien organism that constantly excretes chunks its genome into the environment. It produces an egg with a full genomic complement, and then samples the environment for DNA from other individuals and uses homologous recombination to swap out the old for the new.

Answer 4

Most plants, as well as sessile aquatic animals like corals, do reproduce sexually, but since they don't move about they tend to do it either by releasing their gametes into the surrounding medium or attach them to a mobile proxy species (pollination).

There are also many mobile animals (fish, amphibians, spiders) that do not need to come into contact in order to reproduce - the female deposits her eggs and the male fertilizes them outside of her body. Usually there is some kind of ritual involved to get the female to deposit her eggs, though.

Sexual reproduction does not require the two individuals to come into contact with each other.

The real question is how to justify such a system in an advanced, mobile, intelligent species. Internal sexual reproduction is more energy-efficient and allows greater choice on both the male and female's part.

One possibility is a mostly solitary species where the male and female almost never come into contact. Instead, the female deposits her eggs in a hard-to-open container protected by some kind of 'puzzle lock', and leave clues for the male, who has to figure out how to open the capsule in order to fertilize the eggs. This would allow the female to select for more intelligent males (since only they could figure out how to find the capsule and open the lock). The males, meanwhile, would prefer more challenging puzzles since it would demonstrate better constructive abilities on the female's part. This could accelerate the development of high intelligence without social behavior (similar to that of an octopus), leading to a very alien species.

Another could be a slow-moving species that co-evolved with another, flying 'pollinating' species, allowing them to spread their DNA much further to distant populations (perhaps because the species is prone to recessive genetic diseases). The pollinator species could eventually function like a domestic animal that becomes a proxy allowing them to mate, while getting food in return. Owning pollinators becomes a sign of fitness since it requires the sapient creature to collect more food in order to attract them; having more food allows one to attract more pollinators, allowing them to mate with many individuals at once.

Answer 5

If you want a weird one which actually exists in real life:

One option based on some real life bacteria is gene-stealers.

What happens when a colony of bacteria is introduced to a new environment but is starving?

There's good odds that some of the other bacteria already resident will have genes for handling the food sources available in that environment but how to get those genes?

There's a species of bacteria Salmoneella "LA-22".

It carries a phage in it's DNA. Sometimes the phage activates and kills some of the members of the colony. This isn't much use except when a colony is placed in a new environment with food sources they cannot digest.

Sometimes the phages will infect a resident bacteria but instead of packaging up a copy of the phage it will instead grab a chunk of the original residents DNA.

Sometimes the phage will return to the original colony and pass that gene to one of it's members who than then avoid starving and survives.

Answer 6

What about Lamarckian evolution? Imagine a planet in which multiple species are hosts of the same basic symbiont organism and the latter evolves rapidly during the life of the host.

Maybe assume that the reproduction of both the host and symbiont organisms are somehow linked in a feedback loop. If the symbiont evolves significantly during the life of the host then it would be useful to pass on the final state of symbiont DNA to host offspring.

Ideally, successful combinations of host DNA and symbiont DNA could be passed on and this process will require the exchange of both. The host may retain male and female distinctions, or may be asexual, but the symbiont may then introduce additional classifications and compatibilities beyond that.

Mitochondria can be viewed as a symbiont - and this DNA is only inherited by the female but perhaps its possible to imagine other perhaps less well integrated symbionts (fungi or plants) where things might be different.

After all, most plants have both an asexual and sexual phase which alternate - so combine that with animal male and female and you end up with multiple phases of male and female according to the alternating generations of the autotroph symbiont which would complicate replication of the host (the advantages conferred by the symbiont must be suitably useful for this situation to persist of course).

This is all quite wacky, but then so is the question...

Answer 7

It is entirely possible for retroviruses to transfer genetic material between individuals so it's reasonably plausible to imagine a world where endemic benign viruses have made actual sexual reproduction unnecessary and becoming pregnant is essentially a viral infection. In fact that there is a theory that in utero fetus development is, at least in part, in fact a side effect of a virus not unlike HIV.

In the Mass Effect universe the Asari are an all female species who don't have sexual reproduction in the usual sense but rather use the DNA of others (regardless of species) as a randomising factor on their own DNA.

Answer 8

If it make sense, from the point of view of evolution, that we have to reproduce and to die, it is because we are not able to mutate during our life, we have to create a new beings to allow mutation (and sexual reproduction to allow for mixing genes).

So an answer is : just forget about reproducing, and dying. You can imagine a species which simply clone itself (for example by lying eggs, from which a perfect copy of yourself emerge after a while).

Then if a creature is subject to enough random mutations during its life (e.g. due to intracellular processes or more natural radiation that what we get on earth), its clones can evolved in a different way than the original, and you can reduce the need for genetic exchange.

You can go a step further, by assuming that each member of this specie produce a kind of virus in its saliva (or anywhere else) that is able to inject part of its DNA into cells of other members of the specie, and the result is : when two kiss they actually mix their genes, without need of reproduction.

Note that in this scenario searching for the best partner still make some sort sense, since you will directly "inherit" part of its genetic features.

Note also that such a process can be extend between members of different species.

Of course there is problems, for example if only some part of you partner is affected, he will grow strange unequally distributed mutations. You can avoid that by "sharing" your genes with your partner's clones in a early stage of development (e.g larva or egg) that you can easily affect as a whole.

Answer 9

The Gourmandians have a unique genetic structure. Seventy percent of their DNA/chromosomes is what we have labeled 'base DNA'. The other thirty percent is what we have labeled 'adaptive DNA'.

In a Goumandian's stomach, there are clumps of cells with incomplete DNA. Anywhere from five to ten percent of the total DNA is missing, but always from the adaptive chromosomes. These incomplete cells are also undifferentiated.

When a Gourmandian consumes food, some of the DNA from the plant or animal eaten is absorbed by the incomplete cells. If the newly complete cell is viable, it naturally migrates to an incubation sack and begins mitosis. If it is not viable it drops into the stomach with the rest of the food and is digested.

Once the newly altered cells reach a sufficient quantity, they break up and are absorbed into the blood stream. They travel throughout the body, a few ending up in most or all major systems. There, they automatically adapt into the same type of cell; muscle, bone, organ, etc. They continue to reproduce, having what is best termed as a gentle rivalry with the existing cells. There is not danger or discomfort to the Gourmandian, but whichever version of the cell is more efficient in that role, will win out. Either the new cells with stop reproducing or the old cells will slowly be replaced.

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Would something like that be sufficiently different for you?

You could also have something like a three gender species where the mother contributes forty percent of the DNA, father type A contributes thirty percent and father type B contributes the remaining thirty. Or forty/twenty/forty, with father type B being rare and thus those with good genes are highly sought after and not generally allowed to be in a monogamous (trigamous?) relationships.