How would reincarnation affect the evolution of a species?

Question

For purposes of this question, reincarnation works in the following manner:

• The transmissible personality, memories skills, knowledge and experiences of a person shall be referred to in this question as a Soul.

• During life, the soul develops alongside the body. At death (the moment that the soul's body ceases to be a suitable vessel to hold it, some time after the cessation of all processes of life), the soul becomes separate from the body.

• Some time after the death of its previous body, the soul may attach to a newborn member of the same species. As the newborn matures, the soul progressively integrates with the body and becomes fully integrated at physical maturity. The period of time between death and reincarnation may be as little as a second, or may be many lifetimes, though it is most commonly a relatively short period of time. It may be speculated that one or more 'bad' lives may delay reincarnation, however good lives may also delay reincarnation. There is some correlation between the reincarnation times of a particular soul. Reincarnation is not guaranteed.

• While reincarnation often occurs in a region in which the reincarnated individual lived, it need not always do so, and could theoretically occur at interstellar distances (with lightspeed delays). Reincarnation may occur into a newborn of any race or gender of its species provided that the newborn has a reasonably normal brain.

• A reincarnated individual gains the mental skills, knowledge and memories of the soul which attaches to it.

• a newborn without a reincarnated soul is not born with a soul of its own, it develops one at some point during adolescence.

• The effects of brain injury and/or illnesses such as dementia do not become part of the soul. A soul may be considered to function additively, and has no mechanism for externally applied subtractive processes.

• A soul's content degrades slightly between reincarnations. A soul which has reincarnated many times may typically remember roughly ten previous lifetimes, more if the previous lives were short, or less if the previous lives were long. More recent previous lives are more clearly remembered than older lives.

• Rarely (on the order of 1 in 100,000 reincarnations), a soul may reincarnate into two newborns simultaneously (taking lightspeed delays into consideration). Such duplicate reincarnations lead to two separate souls, the souls do not become one again after the death of both of the bodies.

• Where the species' population numbers are rising, there will be many newborns who are not born with a reincarnated soul. Where the species' population numbers are constant or falling, more newborns will have reincarnated souls, to the point where a newborn without a reincarnated soul is very rare.

Obviously there would be profound social implications for this sort of reincarnation, but they are not the point of this question. However, the social implications will have to be addressed if they could affect the evolution of the species.

My question is, What effect would reincarnation have on a species?

As an example, humans do not demonstrably, frequently and reliably reincarnate. However, for purposes of this question, let us suppose that at the time that hominids speciated from chimpanzees and bonobos, roughly 5.5 million years ago, the hominids gained the ability to reincarnate. If all other selection pressures remained effectively identical and evolution progressed similarly wherever reincarnation has no evolutionary effect, what differences could we expect between real-life humans and reincarnating humans after a similar period of time since speciation 5.5mya?

These differences need not be purely physical, and may be differences in the basic psychology of the species.

Edit

There seems to be some confusion as to how souls work. They do not function as a metaphysical cloud storage that's accessible at any time, like a google drive account that's able to have its content downloaded into RAM relatively quickly.

Rather, a soul's content must be copied into the physiological memory of the body during maturation before it becomes accessible, and any content that is in excess to that which the body can retain is culled according to the usual physiological processes that discard or overwrite less useful memories.

After the body's brain is physiologically mature, the soul isn't able to add much more of its content to it, perhaps only 5% of that gained during maturation.

The process by which memories of former lives may be lost is that memories successfully written into the body are removed from the metaphysical soul. During life, a new soul is written from the body's brain. When the body dies, the remainder of the old soul is copied in a slightly lossy manner to the new soul before the new soul goes on to be reincarnated... when and if it does so at all.

Perhaps 1 in 20 souls do not reincarnate at all, and perhaps 1 in 6 do not reincarnate 'immediately' (within a single typical lifespan of a member of the species).

Answer 1

One thing to consider is that accumulation of experience as a creature ages tends to soldifiy past beliefs and patterns behavior to a degree that they no longer are changeable. "You can't teach an old dog new tricks" as they say and we've all met older people which we politely describe as "set in their ways". However, this can be highly deleterious; the learned behaviors of an individual who has a lifetime of experience for survival in a jungle will not be all that useful when transmigrated to the body of an individual born in a sub-arctic environment.

Its unclear how the body affects the soul in this scenario, but it seems likely that there will be strong evolutionary pressure toward the neuroplasticity of childhood to last into adulthood to allow the individual to learn new behaviors and overwrite old ones that are harmful in the soul's new environment as well as for increased propensity for risk-taking to help the individual overcome no longer appropriate learned behaviors.

Answer 2

Regression in both evolution and also society - and it may be quickly lost.

The important thing to remember about evolution is that it is the genes that are important, not the individual. The incremental improvement of genes relies upon the death and selecting out of non-beneficial genes.

So if an organism, say a flying insect such as a house fly, flies into a spiders web and is eaten - it is reborn and remembers now where the spiders web is, and avoids it.

This pattern repeats many times, meaning two things: The fly never actually dies (although eaten) and does not evolve a keen sense of sight to detect the web, and the spider has to also evolve and step up its game in order to catch the fly (perhaps using more and more larger webs, or creating a situation where the fly has no ability to evade the web even if it remembers where it is). Both organisms adapt gradually, however the fly regressively so.

Basically, the removal of 'survival' imperative from the genome means the genome does not have as much incentive to incrementally improve. The ability to transfer souls would actually over time would actually be lost.

This also happens to Homo Sapiens in society. If someone dies, but their soul appears in another, there is no real incentive to stay alive. Some of the worlds best inventions are based on necessity, and perhaps even the fear of death - remove this and the tenuous web of society may never have formed.

Answer 3

Clever, Strong, but with Poor Memory:

Your species are subject to the same forces that affect anything else. Evolution only drives the development of things that are rigorously reinforced, and leads to the degeneration of traits over time with low or no survival advantage. So what happens with your species with reincarnation?

Your individuals are able to survive despite having a poor memory, because your souls are providing multiple lifetimes of experience to the bodies they inhabit. An organism doesn't need a great memory, but it does benefit from being clever.

Culture would evolve somewhat independently from biology, and I think there would be a strong pressure for a more altruistic culture with collective child-rearing. There may be some social pressure to weed out souls with poor attitudes, but how this would manifest would depend greatly on choices and how your reincarnation system worked.

I'm assuming souls have some options in what bodies to inhabit, so whatever traits the souls prefer will create a pressure for bodies to match it. Everyone wants a clever host. And physical prowess disproportional to the needs of biology may be selected for due to the souls desiring to be strong. I'll assume the souls can somehow evaluate whom they inhabit as well (either through genetics or the ability to perceive the mother).

Reproduction may need to be a very hormone-driven process, as intelligent organisms will intellectually feel less tied to their bodies and will be less driven to have kids. Kids will grow much faster, and need a greatly reduced period of learning, since memories of past lives mean they are ready to be adults intellectually the moment they are born.

Then there are surely opinion pressures that will matter based on what the souls prefer. If souls remember being bonobos, then they may tend to select bodies that are bonobo-like. If they like variety, then the bodies will become dimorphic, so the souls can mix things up between lives. If there are standards of physical beauty, they may inhabit the offspring of pretty females.

Answer 4

Very little change

Since the memory is not immediately copied and can easily be over written, it is unlikely that reincarnated people will have much if any advantage. Therefore, not much change will be imparted upon the species in the form of beneficial mutations.

here lies andy; peperony and chease

In the Paleolithic Era, only around 60% of humans even made it to be 15 years old. So a person might not even know if they were reincarnated, since they are about as likely to die first as they are to survive.

I have no memory of this place.

One thing a prehistoric person might want to remember is the migration patterns of prey, the creation of basic tools, or which plants are poisonous. However, by the age the reincarnation memories kick in these people will probably already know this stuff. Furthermore, the migration patterns of arctic prey is of little concern to someone living in a desert. So unless they reincarnated very close to their last life, it is possible all this information will get overwritten, or at least ignored, since it isn't helpful. Also, if they remember that they were a tool maker in a previous life, but now they are a hunter, if hunting is the better profession, that information isn't very useful.

Intercontinental Tool design collaboration

One advantage would be remembering previous tool designs. This might have a minor effect on the effectiveness of tools over the entire population. This means the whole world would have the most effective bows, slings, knives, and fire starters for their region after a few cycles. This wouldn't require any changes to the genome, and any change that could be made won't help.

prehistoric Career fair

One of the few advantages this provides is if the previous life did a job that is difficult to learn or teach, that can also be done here, the reincarnated individual can do that job. If this person were a leader this also applies. However this has very little effect on the society, and therefore modifying everyone's brains to have more space to maybe remember more lives would have a negative instead of a positive effect.

Results

While a few people in the prehistoric times could use this to their advantage, the effects are too small to make changes to the species beneficial enough to justify the potential cost. The ability to learn from your ancestors would help people, but many people during this time learned from their ancestors by talking to them, and were prepared for the world mostly by adolescence. Therefore expensive changes to the brain would not be worth it for a fairly circumstantial benefit.