Somebody asked about race. And implied that it must exist because Govt and forensic investigators use it but is that proof???

Race theory is just that, theory, and modern people have tortured that concept for political purposes. The inventors of race theory came up with three; (paraphrasing) Asian, black and white. Everything else is just ethnicity but we (especially in the US) have decided to pretend that culture, ethnic origin and race are somehow the same thing.

The divisions between races are doubtlessly blurred, but does this necessarily mean that race is a myth—a mere social construct and biologically meaningless? Even if scientists agree that race is, at most, a social construct, any cursory search of the internet reveals that the broader public is not convinced of this. After all, if an Asian person looks so different from a European, how could they not be from distinct groups? Even if most scientists reject the concept of “race” as a biological concept, race exists, undeniably, as a social and political concept.

"the govt uses it" clearly is not proof. The hypothesis that humans come in a handful of races arose in the 17th century, and was very convenient for "justifying" black slavery. After WW2 it was discovered that pretty much every human has 23 pairs of chromosomes, that you can only (randomly!) pass on one of every pair of yours to a child you make, and that any two humans share at least 99.4 % of their genetics. We even discovered that sometimes two chromosomes of the same pair exchange parts with eachother.

If it weren't for mutations (= quite rare copying errors) we wouldn't be able to tell eachother apart

There are certainly noticeable differences between people from different parts of the world. These differences are the result of adaptations to the local environments. Humans evolved in Africa 200,000 years ago. Many Africans from different regions are quite different from each other. Some, like the African pygmies, are quite short in stature. The East Africans in contrast are quite tall and lean. The West Africans tend to be more muscular. Non-Africans tend to overlook these differences but they are adaptations to a local environment. Being short for example minimizes surface area and being tall maximizes it. People who live in forested regions tend to be shorter because those environments are cooler and the reduction in surface area can help them conserve heat, while tall and lean people with long arms and legs can avoid heat stroke more easily by losing excess body heat more quickly.

About 60,000-70,000 years ago, Africa suffered a severe drought, and a small group of Africans migrated out of Africa and populated the rest of the world. All non-Africans evolved from this group of migrants. The first places these migrants went to was SE Asia. There they largely remained unchanged. The descendants of these first migrants are still very similar to Africans in having dark skin, curly hair and no body hair, except under the armpits and in the pelvic region.

Other people however have changed. These people are descendants of the early migrants that settled in Central Asia (near Kazakhstan) instead of going all the way east to SE Asia. After 20,000 years in Central Asia, some of them migrated to Europe and adapted to ice age conditions by becoming more hairy, shorter, with shorter arms and legs, thinner lips, taller and narrower nose bridges, straight hair, a rounded torso, and more fat under the skin. These are adaptations to cold climates. They reduce body surface and also reduces air flow in and out of the lungs to prevent frost bite of lung tissues.

Some Central Asians migrated to northern Asia, where they also evolved many of the same adaptations to cold climates seen in Europeans. Therefore it is sometimes difficult to distinguish a cold adapted Asian from a European. Both groups evolved light skin tones because their cold environments force them to wear clothes, which block out the sun and reduces vitamin D production. Vitamin D shortage can result in rickets, with broken or deformed bones and even death as consequences. Light skin helps them absorb enough sunlight to avoid rickets.

If people were to stop migrating after they settled in Europe and Asia, then it would be relatively easy to define races, which are differences within a species that is based on geography. To this day, it is still relatively uncontroversial to recognize 3 different races, known as Caucasoid, Africanoid and Mongoloid. However, people have not stopped migrating, not by a long shot. Some Europeans for example migrated back to the Middle East and some went as far west as the Indian subcontinent. The Chinese also migrated south to SE Asia. Everywhere people went, they intermixed with each other. This admixing is strong evidence that we are all the same species. SE Asians are a mix of the dark skinned early migrants and the cold adapted Chinese from north of the Yangtze River. Indians and Middle East people are a mix of dark skinned natives from Africa and light skinned Europeans. Such admixture makes it nearly impossible to classify some groups of humans from some regions as a particular race.

In any case, since the different traits we see in different people are simply the result of adaptations to different local environments, it really does not matter much where people or their ancestors came from. We are all human. We recognize each other as the same species. Therefore it really makes no difference whether we can divide the human species in to different races or not.

Most of the time, you can tell a British from a Nigerian person apart, but that doesn't mean that classifying people into races is accurate. In fact, most biologists don't recognize races or subspecies as a valid taxonomic unit. Hispanics are people that speak Spanish or come from a Spanish-speaking country. They may have very diverse origins, so it doesn't make any sense to call them a "race". These terms are more cultural than biological.

Individuals from different continents may exhibit differences in their skull and body shape and in their external appearance that likely represent adaptations to different environments. That said, at present there's no consensus on whether human races exist, and if they do, which and how many of them are there. In fact, the traditional "Negr0id, Caucasoid, Mongoloid, Australoid" races aren't widely accepted by most anthropologists and geneticists. For one, black people from Africa are the most diverse ones genetically, so it doesn't make much sense to put them in the same category. The Australoid group includes many ethnicities (including the Ainu from Japan, Papuans, some Indians, Australian Aborigines...) that aren't culturally nor genetically related. Then you have terms like "black" and "white" that don't mean much. "Whites" or Caucasoids are people from Europe but also people from India or East Africa that may have very dark skin. "Black" is a term to design people from Africa and also Australian Aborigines that aren't closely related to the former according to genetic studies.

Yes, race is a social construct. There are certainly physical characteristics that resulted from people reproducing with each other over thousands of years. And forensic investigators can use those characteristics to identify bodies. But that doesn't mean that those physical characteristics have anything to do with differences in brain, or psychology. That's confusing "race" with culture. You might as well try to claim that people with big feet are more prone to crime, or that people with long middle fingers are smarter than others.