This is one of the craziest things I've read in a long time: each human can contain multiple genomes. I've actually wondered about genomic variation in a single human before, but I guess I figured that the body somehow prevented if from happening. Apparently not.
Chimerism, as such conditions came to be known, seemed for many years to be a rarity. But "it can be commoner than we realized," said Dr. Linda Randolph, a pediatrician at Children's Hospital in Los Angeles who is an author of a review of chimerism published in The American Journal of Medical Genetics in July.
Twins can end up with a mixed supply of blood when they get nutrients in the womb through the same set of blood vessels. In other cases, two fertilized eggs may fuse together. These so-called embryonic chimeras may go through life blissfully unaware of their origins.
One woman discovered she was a chimera as late as age 52. In need of a kidney transplant, she was tested so that she might find a match. The results indicated that she was not the mother of two of her three biological children. It turned out that she had originated from two genomes. One genome gave rise to her blood and some of her eggs; other eggs carried a separate genome.
Women can also gain genomes from their children. After a baby is born, it may leave some fetal cells behind in its mother's body, where they can travel to different organs and be absorbed into those tissues. "It's pretty likely that any woman who has been pregnant is a chimera," Dr. Randolph said.
If that doesn't blow your mind, how about this?
As scientists begin to search for chimeras systematically -- rather than waiting for them to turn up in puzzling medical tests -- they're finding them in a remarkably high fraction of people. In 2012, Canadian scientists performed autopsies on the brains of 59 women. They found neurons with Y chromosomes in 63 percent of them. The neurons likely developed from cells originating in their sons.
In The International Journal of Cancer in August, Eugen Dhimolea of the Dana-Farber Cancer Institute in Boston and colleagues reported that male cells can also infiltrate breast tissue. When they looked for Y chromosomes in samples of breast tissue, they found it in 56 percent of the women they investigated.
Your mom kept some of your DNA and incorporated it into her own body.
Maybe this acquisition somehow contributes to lengthened female life expectancy?
What the heck do we do with this information now? Along with all the research into how our gut bacteria affect our health it looks like the human body is still quite a mystery.