In my viva exam for my science degree finals over 9 years ago, my examiner put it to me that the man sat next to him (our course organiser, as it happens) was only 10% human. From a microbiological perspective, it would make sense, considering all the commensal bacteria, viruses, protozoa, yeasts, helminths and fungi on his skin, in his gut, in his hair, etc. doing no harm to him at all (in many cases, actually benefitting him) and contributing to a significant but invisible biomass, the human being becoming a living ecosystem for all forms of microbiological life. (I'm still not quite sure about the 10% figure, though. Perhaps he was right.)
It's not quite the same thing at all, but reading that article brought that sense of perspective back into my mind. It's the little mutations that make us all unique and contribute to our own individual nuances from a genetic and biological perspective at least. Some mutations make us more sensitive to certain medications, others give us a different baseline immunity to certain infections. Some mutations dictate to us a varying risk of developing a certain type of cancer, others merely dictate what our bile ducts look like from gallbladder to pancreas. And yet we're still undeniably Homo sapiens sapiens.
, according to this BBC News article. Apparently each of our DNA has at least 100 mutations:
