Why can't you Christians accept that Adam and Eve carried ALL the existing human variation?

I'm atheist. I don't believe in a God. However, Adam and Eve (yes they did exist, and were likely twin mutants) carried ALL the existing human variation in the form of alleles. Each person carries 2 alleles per gene, one from each parent. Adam and Eve can thus carry 4 alleles for each gene. That covers about all the existing human variation. Why haven't you Christians figured that out?