"Social construct" implies an arbitrary choice -- our society decided to split humanity into races this way, but another society might do it in an entirely different way and all such ways are equally valid, which is to say, there are no underlying "real" differences.
Supposing someone wanted to split humanity into arbitrary races based on actual genetics (which is not how the concept of race originally started because genetics wasn't known at the time), it would make sense for most races to be African, since Africa has far more human genetic diversity than all the other continents combined do. The reason races are delineated the way they are now is due to social reasons. (It could possibly make sense when you consider the phenotype though, but due to the outgroup homogeneity bias, I have some doubts.)
Still, regardless of where you set the boundaries between races, there will be average biological differences between them (provided you don't do something biologically ridiculous like classifying whites and Asians as the same race but then classifying their half-white/half-Asian children as a different race).
You're using a definition of "social construct" under which the word "heaps" is a social construct. Sure, given this definition race is a social construct, too, along with a rather long list of most everything. However I think your interpretation of "social construct" is atypical.
It's that time of year again.
If you are reading this post and self-identify as a LWer, then you are the target population for the Less Wrong Census/Survey. Please take it. Doesn't matter if you don't post much. Doesn't matter if you're a lurker. Take the survey.
This year's census contains a "main survey" that should take about ten or fifteen minutes, as well as a bunch of "extra credit questions". You may do the extra credit questions if you want. You may skip all the extra credit questions if you want. They're pretty long and not all of them are very interesting. But it is very important that you not put off doing the survey or not do the survey at all because you're intimidated by the extra credit questions.
It also contains a chance at winning a MONETARY REWARD at the bottom. You do not need to fill in all the extra credit questions to get the MONETARY REWARD, just make an honest stab at as much of the survey as you can.
Please make things easier for my computer and by extension me by reading all the instructions and by answering any text questions in the simplest and most obvious possible way. For example, if it asks you "What language do you speak?" please answer "English" instead of "I speak English" or "It's English" or "English since I live in Canada" or "English (US)" or anything else. This will help me sort responses quickly and easily. Likewise, if a question asks for a number, please answer with a number such as "4", rather than "four".
The planned closing date for the survey is Friday, November 14. Instead of putting the survey off and then forgetting to do it, why not fill it out right now?
Okay! Enough preliminaries! Time to take the...
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[EDIT: SURVEY CLOSED, DO NOT TAKE!]
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Thanks to everyone who suggested questions and ideas for the 2014 Less Wrong Census/Survey. I regret I was unable to take all of your suggestions into account, because of some limitations in Google Docs, concern about survey length, and contradictions/duplications among suggestions. The current survey is a mess and requires serious shortening and possibly a hard and fast rule that it will never get longer than it is right now.
By ancient tradition, if you take the survey you may comment saying you have done so here, and people will upvote you and you will get karma.