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Takeaway A: We can drop the man-equals-caveman caricature. Although human DNA has been found to contain vestiges of our dalliances with Neanderthals from about 50,000 years ago, none of those genomic imprints are on the human Y chromosome.

By the look of it, something specific to the Neanderthal Y chromosome ultimately proved inimical to human health and survival, and so any trace of the Neanderthal Y chromosome was ejected from the human gene pool like a poorly matched kidney.

The immune system analogy may be particularly apt. Fernando Mendez, a geneticist, and his colleague Carlos Bustamante of Stanford University reported that one of the notable differences between the human and Neanderthal Y chromosomes lies in a gene linked to transplant rejection.

Whatever the reason for the purification of the human Y over time, women’s equivalent X chromosome does not appear to have been similarly cleansed, with the result that women on average may be slightly more Neanderthal than men, which could explain our comparative fondness for animal print shoes.

Yes, but apercu B: Hang on to the gorilla suit. From a global genomic perspective, our closest living relative is the chimpanzee, followed by the gorilla. When it comes to the Y chromosome, however, humans look considerably more Magilla than Bonzo .

Kateryna Makova, director of the Center for Medical Genomics at Penn State University, and her colleagues recently determined that if you line up a man’s Y chromosome with a chimpanzee’s, only about 70 percent of the two spans will stick together. Align a human Y with a gorilla’s, and 83 percent of the paired chromosomes will comfortably conjoin.

Looking at nine distinct sets of genes that have been identified on the human Y chromosome, Dr. Makova said, “eight of them are shared with the gorilla, while only six gene families are shared with the chimpanzee. It’s very surprising.”