Why might a species advanced enough to develop genetic engineering start a process by which their own genes, over hundreds of years, would get edited back to resemble their more primitive ancestors? For example, why might humans in the year 2200 release a gene-drive, germ-line retrovirus that reverted humans to Australopithecus?
To display wealth.
Like the peacock's tail, expensive displays are indicators of health and wealth. Think of the expensive shoes, suits, outfits, watches, jewelry, and cars that wealthy people display. It's conspicuous consumption. Or the silly, colorful hats and outfits of the rich in Hunger Games.
If someone, say, from a rich family, were engineered to have 'harmful' or 'ancient' traits that made them clearly distinct from the riff-raff, that would be an obvious sign that they were so wealthy they could afford to sport such traits. It would impress business and social partners.
Although not genetic, there is some thought that head-binding was practiced to make different castes of people visibly distinct in society, e.g. the nobility have taller, oval heads. In order to shape the skull like this, you have to wrap the baby's head basically from birth, so it's a reliable signal.
Think of Chinese foot binding, Victorian corsets, or the elongated necks of the Kayan. These are slightly harmful to the activities of daily life, but thought to increase the beauty and desirability of women in those cultures. If someone were genetically engineered from birth, that's something you can't fake or lose.
And as a germ-line trait, it would be passed to all their offspring.
There could be desirable traits that are wanted.
For instance, many with European ancestors have Neanderthal DNA.
Neanderthal's were believed to have been bigger and stronger, though possibly not as smart as homo sapiens.
By editing the DNA to emphasis the size, strength, skeleton and musculature of Neanderthals (while keeping the brain) you could make people who are better adapted to living in heavy G worlds, or better at labor and opening pickle jars.
Australopithecus were smaller than homo sapiens, but with musculature like an ape, and so might do well in areas where space is limited, such as tunnels, where we'd be living for quite a while while colonizing mars.
A genetic weapon(virus) has been released on planet earth that targets a DNA sequence that is recently new. Animals and vegetation can carry the virus but it is inert and only effects us.
The virus prevents people from having more than one child if any. Humanity will become extinct over the span of several generations.
Our only hope lies in removing that DNA sequence from our DNA. Removing it outright fails and the only option left is to revert to a stable DNA without the DNA sequence that the virus targets.
To create an easier to manage slave class. (You didn't say that everyone had to devolve!)
Let's say that a species lives in a world that used to be temperature. Over time, though, greenhouse gases were released from deposits in the soil, thus increasing the temperature of the planet slowly. Over millions of years, the species evolved to better survive in these warmer conditions (for example, by getting rid of fur).
Now, when they have developed this genetic engineering, an asteroid hits. Suddenly, temperatures drop substantially, bringing the climate back towards where it was originally. The species doesn't have the technology to adapt to this using machines - but they can "devolve" back to having fur or other characteristics they had gotten rid of when temperatures rose.
I don't know the details of the members of the genus Australopithecus, but I do know that given that they dwelt in Africa, they were most likely suited for hotter climates than many humans are today. So perhaps we should use the reverse of my example - a case where it suddenly gets much hotter, not much colder.
To ease and make safer childbirth.
Modern humans evolved smaller birth canals as a consequence of walking completely upright. Earlier ancestors weren't as upright as we are today, and therefore could have larger hips and birth canals. This made childbirth more dangerous for modern humans.
If women were engineered to have larger birth canals, ala our ancestors, this would make childbirth safer for both the mother and the infant.
In Star Control 3 game (which was made by different studio and was so unlike Star Control 2 that many fans refuse to acknowledge its existence, but that's irrelevant) Precursors are revealed to combine genetic memory with sapience-removing de-evolution to hide from cosmic horror which periodically visits the galaxy, eats all the sentient species and seeds new sentient life.
Note: SC series in not a Mass Effect ripoff, if there is direct relation, it's other way around: SC2 is pretty much a ME done 15 years earlier.
Reasons that aren't a direct inspiration might be:
- Australopithecus become unduly glorified (just like terrible times long gone are glorified because most people only look at glamorous slices of those times: almost everyone wants to be a medieval king, but if those times came back almost everyone would be a medieval peasant) because of in-touch-with-nature-something or other nonsense and people want to become like them.
- Some group of people volunteers themselves and their offspring (heavily violating modern ethics) for sake of recreation of extinct species.
- Instead of recreating our main ancestors they are trying to recreate Homo neanderthalensis whom Homo sapiens sapiens did briefly interbreed with, before driving them extinct. A little bit of neanderthal genome is present in modern humans.
- Maybe Australopithecus had some adaptation which are going to be important? Incoming hot age perhaps?
For example, why might humans in the year 2200 release a gene-drive, germ-line retrovirus that reverted humans to Australopithecus?
It's the Greens. Not all of them, but a lunatic offshoot. Think Ted Kaczynski with a genetic engineering degree. In order to get humans to abandon the technology that is destroying the planet (this Ted's words, not mine), he reverts everyone to a more primitive version.
Australopithecus were apparently about as intelligent as a chimpanzee. While they might be able to operate some technology, they would not be able to maintain it. Over time, the power plants would stop producing electricity and virtually all technology would cease to function.
It is of course up to you how successful he is. Perhaps the retrovirus is eradicated before it does much damage. Perhaps it reverts everyone.
For finding "Adam" and discredit popular religions.
Different de-evolution stages could also provide historical information about Earth (museums with highly priced tickets could have a live de-evolution show). DNA sequences found in old human remains could also be compared in order to validate and understand why certain "evolution" occurred.
If the Earth does not exist in the year 2200, by feeding rescued living beings samples to the "de-evolution machine" will allow to map and recreate a similar planet from scratch.
I don't think it would happen.. for humans to evolve Backwards... it would mean that those possessing the genetics to 'revert' would need to breed... humans as a species are very picky on who they will and wont breed with. if someone was to bear the traits of an early humanoid I don't think there would be a long line of people wanting to procreate? therefore the Genes would not be passed onto the next generation.
I'm not saying We humans don't like to procreate with those that have 'faulty' genes or such but I don't think many would be willing to procreate with a person resembling an early humanoid?
It could happen with other Species if there are those resembling earlier species traits it could happen. Some species of fish for example have lost their eyesight by being Cave dwelling with very little to no light. Eyes were not there at the very early stages of life so they have technically reverted back to an early genetic variation where Eyes were not in the Genetic make up.
This could happen to a population which was artificially isolated into a small region, to which it evolved to. If that isolation were to be ended, and that species finds everything it had adapted to was wiped out, the shortest path to survival could be to go back and try again.
This almost never happens in natural evolution, because nature prefers not to be wasteful. It'd find a use for those genes rather than just tossing them away. However, your question is of an advanced species which can do genetic engineering. Such a species is more likely than nature to make a decision to take their genes down a specific path, only to find that they had misanalyzed the situation, and these new genes were a complete evolutionary dead end. For example, you might devise genes which appear to adapt faster, using Turing machine style discrete thinking, only to find that these new genes always enter a loop, unable to evolve against the ever evolving environment.
In such a situation, a species may throw their hands up and say "nature knew best," and toss out all their hard work. They would likely try to adapt their new genes to break through the hurdle, but that may be impossible due to time constraints or mathematical limitations.
Hmm.. excellent question.
When I first read it, it occurred to me that, after the population wars from the exponential growth of humanity, and genetic tampering of both food and population, it was discovered that, at some point in the evolution of humanity after gaining sentience, a flaw appeared in the genetic makeup common to all humans. This flaw was in genes so integral, and so wide-spread, that even gene therapy could not repair the damage without the likelihood of irreparably damaging the DNA. Without knowing it humanity had tailored a series of events that would lead to the death of 99.999% of the population within a year of the first death.
It would then be the only chance for humanity for them to wake dormant genes and essentially reset the human genome, hoping to give them a chance to avoid the genetic breakdown.. plus, this time the humans evolving wouldn't have oil or coal to abuse.
But truth told.. I have to think the most likely reason would be vanity. Right now we look at people from the 80s and wonder what the hell could make them think that hair was ok. But to them it was.. by the time humanity has discovered a million new vices, it would probably be in style to look like a neanderthal, since everyone else would be custom tailored to look.. "perfect"