Could a new Adam and Eve survive and thrive?

I’ve been watching Fringe for the first time and in one episode the 2 principle characters become very close to being the only 2 humans left in the universe. The antagonist even refers to them as the “new Adam and Eve.” The woman on Fringe was in her mid 30s but let’s pretend she’s in her early 20s.

Given this scenario how likely is it that 2 healthy humans could interbreed to the point where their descendants are able to grow, thrive and generally live healthy lives? Assume no gene splicing or designer babies; and that hunger, thirst, shelter and protection are not immediate concerns.

What else is left on earth? Can they just move from house to house as they see fit? Grab any tools they find in abandoned stores? Kill or capture feral cows?

If they have to start in a prehistoric world, then no. Man has evolved away from dealing with that.

In the show it’s more like a Garden of Eden scenario, but they’re onboard a ship with undefined cargo, so we can assume the ship has enough resources on board to keep them and many potential generations in stock of all essentials, if the generations actually survive.

In terms of reproduction, the high risk part is right now while there is zero redundancy. If he has weak sperm or she dies in childbirth of her first child who’s a boy? It’s game over.

Once there are a half-dozen breeding pairs (i.e. 1-1/2 generations later) that critical risk drops away.

Inbreeding leading to genetic problems is unhelpful long term, but it’s nowhere near the closest snake.

Even aside from any question of inbreeding causing genetic defects, the children and grandchildren would have to overcome the natural aversion to having sex with close relations.

Is that actually natural or cultural?

Possibly it’s cultural. But the original couple are from our world and have the aversion.

If they want the human race to survive, they can keep their mouths shut.

My guess is natural, since other animals seem to avoid it as well. Here’s the first cite I found:

Scientists Find Mammal Species that Practices Incest Frequently | Tech Times.

In my experience, cats and dogs do not avoid incest.
As to the scenario we are pondering: I would think the Eve person would need to start getting pregnant as soon as possible and as often as possible.
But if they are on a ship, what kind of manpower does that take to run and maintain? Can the Adam person handle it mostly alone, since Eve will often be pregnant or nursing?

I think it would fail, resulting in humanity’s extinction.

There never was an “Adam” and “Eve”. Species do not evolve that way. Instead, entire populations of thousands of individuals change over time, becoming reproductively isolated from other populations, but retaining enough genetic diversity to not suffer overly from bottlenecks. (Sometimes this fails, and we get tragic cases like the cheetah.)

Animals cannot understand inbreding consciously. However, the vast majority of animal species go out of their way to avoid it anyway. For instance, male ground squirrels will leave their home territory and go on a dangerous journey before they find another colony full of potential mates. If they are successful, they leave the next year (they grow up in less than one year), which means going on a dangerous journey despite having found a bunch of receptive females. If they are unsuccessful, they stay. They don’t consciously understand this, but if they stayed they might end up mating with their own descendants.

We don’t know if the humans would breed with each other given they have no other choices. However, they would likely lose the ability to breed in a few generations. Likely, not necessarily: some species, such as domestic hamsters, have persisted despite such unfortunate origins. (Supposedly all domestic hamsters came from one litter, presumably full or half siblings.)

Putting genetics aside, humans are social creatures. I do not believe a mere two humans could raise numerous offspring while essentially living a caveman lifestyle (hunting, gathering, dealing with bad weather, temporary food shortages, long term skill shortages, and the like, while the 21st Century technology decays around them). I honestly doubt the next generation would even make it to adulthood. Accidents, starvation, disease, or bad weather would likely kill off at least one human before this becomes a real issue.

Please tell me about the cheetah (or please be so kind to give me a link about it)!
I am intrigued!

An example:

This has actually been tested with skin grafts. Most likely, if you got a skin graft from a first degree relative (child, sibling, or parent) your immune system would reject it.

Adam and Eve lived in a paradise designed by God to have them be fruitful and multiply. From later in scriptures were we return to such a state, there will be no disease, this would seem to indicate no genetic diseases as well.

After expulsion from the Garden of Eden God was still with them in the be fruitful and multiply things (it says God helped Eve have Cain), so God was still in this be fruitful business. Additionally during this time humans lived hundreds of years, and evidently had the direct help of angelic like beings living among them, so we can assume significantly advanced technology, or magic - it’s really impossible to distinguish between them.

With your caveat no gene splicing (thus no magic), and no life expencancy increase to 100’s of years, I’d say with what we know about genetics 2 people would not be enough to restart humanity. However we do have Noah and his family which was 8 people (saved through the waters). After which God lowered human life to a max of 120 years from hundreds. God did once again proclaim to those 8 be fruitful and multiple, so given the above we can assume God had assisted in at least the next generation. Thus the prodigy of Noah’s family, or at least ark-mates would seem to be perhaps a reasonable but minimal number to restart humanity.

I think the biggest problem would be that, unless at least one of them is a physician, there is a high probability that Eve will die in childbirth, before they have enough children to give the community a safety reserve. After Eve dies, they have to wait a decade and a half before the next generation is capable of breeding. Lots of opportunities for extinction there.

In the Israeli kibbutzes, the expectation was that creche-mates would be very likely to marry. They almost never did. The leading explanation for this (of course, direct evidence would be hard to find) is that there is a genetically determined resistance to marry “siblings”, defined as persons you grew up with. So the best method to prevent this from interfering with reproduction would be to keep all the kids as far apart as possible.

If they reproduced constantly (and the woman survived long enough) the kids would likely have genetic problems. They should be encouraged to choose as many partners as possible and hope for the best. I am not a geneticist but I wouldn’t rate their chances highly.

Neil Stephenson’s Seveneves starts, as the title suggests with seven woman and that seems to be enough. Of course, that is all fiction.

“A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, analyze a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, die gallantly. Specialization is for insects.”

Lazarus Long
Robert Heinlein

This is what humans have more or less lost, and would doom the species in the scenario in the OP.

I could easily do all of those things except write a sonnet. I mean I could write one but it would not be that good.

The boy stood on the burning deck, his feet were filled with blisters . . . :slight_smile:

A normal childbirth without any complications could indeed be handled by a non-professional or even the woman herself, but if things go sideways, you’re gonna want a medical professional on hand.

Don’t “factual questions” imply and require “factual answers”?