An immutable reality
People's personalities are largely based on self-identification. Language, accent, social background and even their football club. All those are conditions partly imposed by the environment, but ultimately accepted by the individual. A working-class Londoner can change his accent for a posher one, move out of the city, start watching cricket instead of football and, in the end, live indistinguishable from a group that has little to do with his birth origins.
It is evident though that some physical realities are immutable. While things like height and build may come to mind, race and gender are definitely the most crucial of them. This text is not part of a gender studies lecture, so we will just leave that aside for the moment and focus on the most basic form of self-identification within the human species: race.
Do races exist?
That is a fair question to be asked. To understand if they exist it is first necessary to look at the definitions of the term. For a long time "race" was used as the generic term for physical and cultural variations observed between different peoples, thus not constituting a proper scientific concept. It was later used in anthropology to define human populations, where distinct physical traits that were observable and measurable could be attributed to partial genetic isolation. The more current use, although much more restrained, is to see race as a synonym for subspecies.
Subspecies, in turn, can be defined as:
"an aggregate of phenotypically similar populations of a species inhabiting a geographic subdivision of the range of that species and differing taxonomically from other populations of that species" .
Many of the different human populations do fall under this definition. A native man from southern Europe can be distinguished with 100% certainty from a man of sub-Saharan origin or from Eastern Asia. A genetic test can also confirm this visual differentiation.
This subspecies status is not so clear for all variations though. For instance, a northern German may seem very different when compared to a southern French. However, in the grand scheme of things, both are physically very similar and genetic differentiation becomes less evident. Anyway, the aim of this article is not to delve into taxonomy technicalities, but to contextualize in terms of science what even the layman is able to recognize.
Race, the divisions within the human species, is an evident factor. It does not depend on language, history, religion or other cultural factors to be determined. The major racial divisions can also be independently verified by different means: visual identification, skull measurements, genetic tests and many others.
This reality is so strong that it was necessary for the whole scientific establishment to unite under one chorus: "races don't exist", to counter it. This mantra can very often be heard in discussions, as it is now "scientifically proven" that races are only made up, and that you should only listen to the reasoning of "specialists". The famous "there is no race gene" and "we are 99% alike" kind of sentences are deeply stupid arguments from a scientific standpoint, but they are designed specifically for sentimental appeal, which they do quite well.
Why do scientists claim the non-existence of races?
I believe this can be attributed to several factors (and none of them scientifically valid), the main ones being:
1 Personal bias:
Scientists already come with personal bias to their first year of university and there they have courses on the ethics of science. They are taught that to pursue and publish scientific truth is not always the correct thing to do, and that their discoveries may have bad consequences for society. Although that point is quite true, most people still believe that scientists are "impartial" and thus accept their interpretations without any questioning.
Being a scientist is a career, one that needs a good deal of money to make it work. Funding can come from government or the private sector. Either way, nobody wants to sponsor "bigoted" PhDs. Conversely, scientists who make PC, good for headlines discoveries have access to more money.
3 Institutional pressure:
Even if a researcher accepted to work with considerable less funding, greater pressure would come from his own scientific community and university. If the published findings were too "offensive", then he would lose his job and be no-platformed for the rest of his life .
How to argue for their existence
You cannot use good science to confront bad science in a conversation, for any topic of discussion really (unless you are all specialists in the area). This becomes a much stronger recommendation to follow when the whole scientific establishment is against you. You muster enter these arguments accepting that in no circumstance people will "convert" to your perspective, you should only try to disarm their programmed answers and build something up from it.
A good example of an argument to use is "if it wasn't of humans we were talking about, there would be no question about existing different races", which seems to do the trick. This highlights that you are not confronting the establishment itself but pointing out the real reasons (social reasons) why they deny your perspective.
Against argument such as "we are 99% the same", do not even try to address the point directly, but only ask: "what would be, in your opinion, a percentage that is too low?", you can then proceed to point out that the human genetic similarity with a banana is of 60% .
If someone calls you a racist (bigoted, nazi, etc.), just skip this as nonsense and ask for a more civilized level of discussion. Never try to play the revisionist on any topic (unless that is what you want to discuss)! The main idea to take from here is: if the goal is to "win the argument", you first have to make your points acceptable.