Future People on Earth

Question

I watch the TV show The Last Man on Earth and there is only a handful of women and men living. In the show the few are trying to conceive. They haven't covered how eventually they will have to inbreed a generation or 2 away.

In the event that mankind is wiped out to a handful of people and not enough for genetic diversity could the amount of people needed to repopulate the Earth be reduced by using Gene Editing and Modification?

Although several people survives in remote parts of the world only a few had good DNA, age and disease free to procreate.

With the help of a geneticists and a salvaged lab could DNA be modified to have your siblings baby but healthy?

As science progresses the plausibility of Adam and Eve giving rise to a whole world sounds more and more realistic to me. Can humans be so genetically perfect not to have defect for many generations?

What is the minimum human population necessary for a sustainable colony?

Answer 1

Easier, More Effective Methods Available

Genetically modifying people to inbreed doesn't make much sense when there are better options on the table. The easiest we could do with today's technology is to freeze sperm and eggs so that you can artificially rejuvenate the gene pool periodically. On top of this, if the planet is smacked hard enough to kill off that many people basically the entire ecology of the planet is dead too so there really isn't any way for humans to survive or maintain a high level of technology anyways.

Answer 2

Inbreeding is only a problem if there are genetic diseases in the DNA. If you remove all traces of genetic disease then inbreeding isn't a problem (until new mutations cause new ones anyway).

That said, they'll be blown back to the stone age so a scientist's time would be better spent building a better bunker or spacecraft than building incest resistant people.......

Answer 3

The trouble with inbreeding is all about the fact that we have TWO copies of every gene; because we get one chromosome from each parent.

So; if you get a mutant allele that doesn't work from one parent, the chances are you won't even notice if you got a functional version from the other parent. This happens all the time.

When two people who are closely related have children, the chances of the child getting two bad copies of a gene increase very substantially, because both parents have a recent common ancestor who gave them their genes.

Also, the idea of 'genetic diseases' is not entirely correct. For any gene, there are thousands of alleles; each one might differ by only one nucleotide. Some are more or less functional but since the function of most proteins (proteins are encoded by genes) are very complex, each allele can be more functional in one situtaion and less functional in another

Consider the sickle cell gene; it makes a 'faulty hemoglobin protein' which aggregates at low oxygen tensions. But that same protein is protective against the malaria parasite (which lives inside red blood cells). So the same allele of hemoglobin is harmful (can't carry oxygen as well) but is protective against a very nasty disease for which there is no cure. Most alleles are like this; they have advantages and disadvantages.