Genetic diversity in an interstellar society

Question

In my project, which portrays a modern take on the classic Asimovian "human empire among the stars", I have a society connected by stable wormholes which are as instantaneous as the portals in the game ... Portal. Energy is practically boundless because fusion has been mastered, and hydrogen is everywhere in space.

The time it takes to travel from world A to world B is only the time consumed going from A to the edge of A's solar system, and then from the edge of B's solar system to B. Fusion-powered ships could do this in weeks or possibly days by most reckonings.

[Question has been refined after this point!]

Goods and people travel between these worlds with the overall expense, regularity and ease with which early 20th century people would travel between continents. Not something one would do every week, but something almost anyone would possibly do at least once in their lifetime if they wanted to.

Genetic engineering is of course a very old (and thoroughly perfected) science at this point. However, most cultures abstain from its use beyond negative eugenics (the elimination of congenital defects). Others used it early on to shape the founders of settlements to better thrive on worlds that while habitable without terraforming, were not earthlike.

So, with all that said, my question is, would natural humans, which aren't actively engineering themselves on a genetic level, and which are no more physically isolated from other groups than continents were before jet air travel, still result in new races of human beings?

By races, I mean the fast and loose definition of a "race" - a group of people with unique physical traits that stand out and visually identify them as members of such a race. Traits that consistently are passed on to future generations.

Of course, if left isolated, any group of people would, over many generations, result in such a thing. But with the lack of isolation, would it still happen?

I hope this didn't sound ... racist or ignorant somehow due to my wording. I botched the question originally in trying to avoid that.

[Another quick edit]

When I first posited this question, I hadn't settled on an exact number for the age of this empire. I knew I wanted it to be quite old (by our standards). I've settled on 31,000 years. Which places it roughly 33,000 years into the future (this empire was not an entity immediately upon colonizing our own solar system or nearby stars reachable without the impossible concept of FTL or the wormholes later used).

A decent time frame may help with this question if anyone has anything further to add.

Answer 1

After 33,000 years of being largely isolated on their respective planets, your populations would be very different for these reasons:

1. Natural rate of mutation. Background radiation, cosmic rays, and even natural environmental chemicals all can cause chance mutations, which accumulate over time. After 33,000 years every planetary population will be significantly genetically different from every other human population. Hair and eye colors seem to be random mutations, and 33 millennia is plenty of time for something to happen.

2. Evolution based on selective pressures, like other posters have stated. People's bodies will make progress adapting to their environment after 33,000 years. In hot climates, people will be shorter because their ratio of body mass to surface area will be better for cooling off. The taller people could have died off from being more susceptible to heat exhaustion. At high altitudes, people's lungs will adapt and their torsos will be V shaped. In cold or dry climates, people will have bigger noses to warm or moisturize the air before it enters the lungs. Melanin in skin helps regulate how much UV radiation a person gets, which contributes to a healthy amount of Vitamin D. If there's not much food on a planet, people will be smaller. If people have to physically fight for survival, the strongest, fastest and hardiest will be selected for. The most intelligent or compassionate probably won't be. I don't think people will survive on high gravity worlds because their circulatory systems will have to work so hard they'll die early, and the strain on their cartilage, spine and joints will break them down. On lower gravity worlds, the people might be taller and live longer, but have less sturdy bones.

3. Epigenetics. Epigenetics is how your DNA strands switch on and off due to nutrition and environmental stimuli. People have a lot of DNA that they don't use, but under the right conditions their DNA will change the way it expresses itself. Poor nutrition will cause unhealthy DNA activation which leads to illness. Good nutrition and stimulus like exercise, sunlight, etc. causes illness-causing DNA to switch off and health promoting DNA to switch on. Exposed to an alien environment, people's DNA might switch on strands for a better immune system, fewer sweat glands, altered receptivity to particular nutrients that are in the environment, and so on. This could possibly result in different complexions, hair textures, or health problems.

4. Nutrition and Gut Bacteria. After 33,000 years, the population on a planet will have adapted to the food available or died out. In the last 10,000 years on Earth, populations developed varying tolerances to different foods according to what their ancestors consumed. Gut bacteria drives a lot of this. If the food on a planet doesn't give good gut bacteria something to live on, people are going to have shorter, unhealthier, more miserable lives. This could cause vitamin deficiency diseases, mutations, and medical syndromes that the people think are normal.

To give you an idea, Europeans and Asians started progressing down distinctive paths around 40,000 years ago. Your timeframe is right about there. For true speciation, where the different planetary populations are so different that they can't interbreed, it would take from 100,000 to 500,000 years of only reproducing with their planetary group.

Answer 2

You say that your societies practice two forms of genetic engineering: Eugenics and modification. You don't explain how they eradicate undesirable traits, but it seems like they perform genetic tampering on zygotes rather than anti-fertility treatments and genocide.
One thing you should consider is how they define a certain trait to be less than optimal. Of course, it seems like you know a bit about trans-humanism, so you probably already have determined their criteria for that.

Have your Terrans homogenized their own population? Or, have they bred different subspecies for different biomes on the Earth? That is, more or less, how many of the modern “races” came about: starting from a certain gene pool, which migrated to a new area as–yet uninhabited by other humans, where some traits died out while others survived. Natural selection.
Darker skin nearer the tropics and the north pole, where more ultraviolet radiation got to the skin; paler skin where sunlight was less abundant and vitamin D deficiency became a factor. Higher altitudes making for less oxygen in the air. Hotter climates — wetter climates — et al. Some of those traits are less invariate than others: People have some predispositions to, e.g., athletic endurance, sure, but that can be mostly overwhelmed by training, diet, and the like.

Anyway.
It would seem probable to me that they have done so on Terra if they are doing so for other planets. As such, they would probably recognize that the viability and advantages of genetic traits are quite reliant on environment: what is advantageous in one place could be lethal in another.
As such, those people who know and do the genetic engineering wouldn't have any misconceptions about genetic “superiority” — but others could.

A certain degree of pride in ones' genetic traits might even be fostered: attempting to promote friendly competitiveness between colonies of the Empire, the colonists begin to think that their own achievements are the result of better genetic stock.
Perhaps.

As to whether the Terrans, or any other of the planetary subspecies, would be interbreeding? I doubt it; would the genetic engineers permit such things to occur, or would they be carefully controlled?
Regulated mating is tantamount to fertility restrictions, but some groups may think it is easier than allowing anyone to breed and then pruning and tailoring the offspring later.

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So, I hope my little answer isn't too speculative for this question and its science-based.

Genetic diversity? Yes — quite a plethora. A plethora of populations, you could say.
Breeding between colonies? Unless that is how they conduct genetic engineering — no.

Answer 3

I think isolation is still there; occasional visitors from off world notwithstanding. Our features are environmentally driven: The caucasian nose, skin color, eye color and hair are all adaptations for a colder climate. Our skeletal structure and muscles are clearly adapted to deal with our particular gravity. Just look how differently animals evolved in a near weightless environment: The ocean. You won't get anything like an octopus on land; you could easily get much closer to that on a low-gravity moon.

If the majority of people never leave their planet for more than a total of a few months out of their lives, then selective pressures exist for them to adapt to their planet. They are effectively isolated there, with their gravity, sun, insects, food, atmospheric pressure -- that last influences hearing design, lung and breathing musculature design, even blood design in isolated high altitude tribes.

The presence of visitors and inter-breeding will not change what is optimal for that planet; the offspring have lower chances of survival without the traits that could save them on that planet, that is why we call it an evolutionary pressure in the first place. Permanently migrating to another planet has the same outcome: Not quite a fish out of water, but a fish at a slight disadvantage in a different pond with less/more oxygen, different and less nutritious food, objects out of reach for taller natives or awkwardly placed for shorter natives, and so on.

If you engineer all your planets to be indistinguishable from each other, and do something to encourage migration between planets so maybe 20% of the population on any given planet is from off-world, then you likely have no significant differentiation or genetic drift. If the planets are all livable but different, like places for people on Earth, and you keep your migration light (as you specified, maybe around 1%), then you will most likely develop distinct races.

Answer 4

It depends on how different the planets are from one another If the selective pressures are different then differences in the population will arise.

It also depends on how you define ethnicity. Ethnicity has no hard and fast biological definition, it is more or less opinion. Ethnic differences could mean a lot of things, so you should qualify what you mean by "ethnic".

Answer 5

All living things adapt to suit their surroundings simply because those who don't have less chances to pass on their genes. All that is necessary for the emergence of new ethnic features is an environmental cause for a less wide section of the population to be able to breed and time. That being said, with such an ease of travel across the stars, you would need a reason for certain groups of people to be forced to live in these less than ideal and identical situations.