human biodiversity (hbd) is very simply the diversity found among and between human populations that has a biological basis.*
each of us is biologically unique. our genomes, our phenomes, our patterns of gene expression, our epigenomes, our microbiomes — none of these are ever exactly the same in any two individuals, even identical twins. yes, you are a special snowflake! you’re not even the same person today biologically that you were when you were six — or sixteen (unless you’re still sixteen, of course). for one thing, your patterns of gene expression as an adult are quite different from what you experienced as a toddler. each individual human is biologically diverse when compared to all other humans and even across his or her own lifetime. (got that last idea from steve sailer, btw.) and while we’re at it, you’re biologically diverse within yourself, too — cell by cell.
additionally, groups of genetically related individuals can exhibit average differences in various biological aspects (see more on this here). for example, immediate family members are more similar to each other genetically — and, usually, phenotypically — than they are to strangers. moving outwards from that circle, extended family members are also more similar to each other genetically than they are to strangers, although less so than are immediate family members. and the circle can be extended even further to: clan and tribe members, traditional villages and regions, ethnic groups, and races, until we reach the human race where we start comparing our collective biological traits to those of other species: primates, mammals, vertebrates, life on earth…. biodiversity in humans also exists between the sexes. remember that the biodiversity found in all these populations — which don’t necessarily have well-defined boundaries — includes features like epigenomes and microbiomes in addition to genomes.
hbd research is conducted in numerous academic disciplines and their subfields such as biology, genetics, medicine, neurology, psychology, and anthropology. hbd research also draws on social, historic, and prehistoric data related to human populations. (there is no separate academic discipline known as “human biodiversity.”)
*i’ve stolen that very elegant definition from claire lehmann.