^{Daily mail Picture of sisters that had Kids of mixed race,
phenotipically seen as of different race by most}

Race

A position shared by most geneticists is that the category known as race is not specially useful.^[1] Still there are advantages to the self identification of phenotipic characteristics in the medical field.^[2]

Such categories are arbitrary, and despite their usefulness -Which can be traced at not more than 3-400 generations^[2],[3]- they are not a particularly meaningful way of dividing human genetic diversity. The idea of having clear-cut sets would be to identify the number of populations where the individuals are homotypic, this means of a single type.

The modern concepts of race come to us from the Victorian era, when essentialism was rampant.^[4] A more recent equivalent of this comes to us in the form of dividing human populations by their position in continental masses (Asian, African, European) to find correlations and compare social outcomes like income, health, criminality and I.Q.^[5]

Such approach disregards the interactions of environment, biology and emerging properties like social, economic and political changes.

Cline

The discontinuous perception of genetic variation among individuals across the land of the world has suggested the existence of >350 different genetic microsatellites. This summed to the phenotypic variation could suggest the existence of 350 Human races in the world, 250 of which reside in Africa alone.^[6]

What most people consider "race" is a social construct, literally skin deep. This is, the ones used in every day are marginally related to what geneticists mean by race. These categories are assigned by identification rather than by ancestry. Haplogroups are a combination of haplotypes, which is a form of identification of distinct subgroups that can't easily be traced by just observation and shares an overlap with the everyday concept of race. They share a patrilineal or maternal common ancestor.^[7]

^{In this Haplotype map of Y chromosome one can trace for instance the}

A deme is a distinctive group between a species where reproduction is still possible but each group is subjected to different selection factors - eg. birds with different mating calls- If there's a continuous variation across geography in the two extremes of the phenotypes, then this is called a cline.^[8] A cline is a subgroup of deme where there's a gradual transition of the characteristics without discrete differentiation (example: hair color)

The description of what is a species, subspecies, cline, deme is mathematical.^[9] We use the Population's fixation index (F_ST), developed by Sewall Wright. Is a way of describing populations substructure, to see if the group is genetically homogenous by examaning the variance in allele frequencies between population and on the probability of identity by descent.

Which translates in practical genetic data to Where and are the average number of pairwise differences. By studying SNP of autosomal observations about the kinship distance of populations have been made.

The F_ST of modern humans is around 12% based on the International HapMap project's data. this means that 88% of all variation among humans is shared by all groups. The initially proposed cut for when a population can be classified as valid if the F_ST for the subspecies is >25%. This can be interpreted that the kinship as seen by such measure between two people of the same subpopulation is slightly higher than between two siblings of mixed populations parents 0.125-0.109 respectively. This illustrates the extreme of the subspecies classification of humans.^[10]

In contrast about 1/3 of the time a person is more phenotypically similar to someone of a different population that to a member of the same population^[11]

Any conversation must always relatively below the subspecies term. When there can be a spread in F_ST such that nonrelated individuals have a kinship to grandparent and child or two mixed race siblings, this is a testament of how most genetic variation is bigger among individuals than due to race.^[12]

One can find that even the most white isolated populations in America have at least 3% african ancestry while Africanamericans have 20% white ancestry.^[13]

We can have millions of races or one. As anything bellow subspecies is an arbitrary statistical correlation. We can talk of clines or demes and is important to remember that this classification is put there by us. It wasn't already there, so to speak. Like dividing world history in eras, making a continuum discrete to make it simpler to grasp.

Are there good ways to put the limits to such arbitrary divisions?

For this one can use the principal component analysis, on the eigenvector one plots a wide combination of genetic markers from non-coding regions and they have not been selected for.^[14] This would mean that we are most likely observing the natural genetic drift of a population not due to environmental and sexual selection.

^{Admixture of two populations, where population C is a recent derivation of B and D, with a large dispersion.
Consistent with the Thai, Chinese and Japanese populations in the Haplotype Map [15]}

Each point in the graph represents a group of individuals drawn from a different population. If a population is a distinctive deme, you would expect that by sampling across all intermediary geographical positions between two distant places you will find genetic discontinuity.^[16]

In the case of humans what you find is that the more distant they are, the less related. Which suggests humans are a cline and genetic exchange of material flows continuously. This cline distribution can be seen across the world with regional discontinuities marked purely by geographic isolation and even at the local level there's variation -particularly in africa^[6]- if one wants to draw a hard discrete differentiation there are not more than 1-2 groups. Otherwise one would have to accept hundreds or even thousands of races (e.g., at least 20 distinctive races of Jewish people that would overlap with groups that don't self-identify as Jewish)^[17]

If we instead go by inferred populations we could divide the sets at k=2, 3,4...350; being 4 the commonly used division in Europeans, African, Amerindian, and Eastasians. Again, this is arbitrary, mostly due to social construction and reflects a particular perspective on a cline.

One can use a division to show a deme. This doesn't reflect anything about the populations but about what we are trying to say about our particular division. It can be useful but always remembering is arbitrary.

---

I'm planning on addressing IQ and Race in a future post. It's a subject full of thorns that most don't find any usefulness in yet is an interesting application of how good statistics of a superficially treated subject can be damaging.

Also T=-7 days for my departure to the Steemstem Meet up (With scales it will take me around 15 hours by flight plus 7 hours by train, a slightly long trip). Super excited!

REFERENCES