Over at Genetics & Health Lei is commenting on the genetic character of Shiloh Jolie-Pitt, and referencing an old post of mine on this topic re: genetics. It is all pretty amusing, but, here is a prediction: The level of spontaneous abortion should be increasing in modern populations "Spontaneous abortions" are the half of pregnancies which naturally terminate without the woman ever knowing. It is often said that modern populations are subject to relaxed selection, that is, the genetically less fit can, and do, reproduce at a healthy level. Over time this should increase the genetic load upon the population and the frequency of deleterious alleles increases...but does it? The point I'm trying to make is that there is still the bottleneck of implantation and early embryonic development at work. The reality is human embryos are subject to extremely high rates of chromosomal abnormalities and other assorted mutations, trisomy 21, which leads to Down Syndrome, is actually a rather a mild form of karyotypic malformation. Most of the others are lethal and result in spontaneous termination. The point is that the human population is rather large, I'm not that scared of a mutational meltdown. Additionally, we don't really know the exact frequency of spontaneous abortion because of its nature, so we probably don't know if the rates are increasing to purge the gene pool.