Different breeds of common domesticated animals such as horses and dogs clearly show different behaviour, instincts, social relationships and similar, due to their biological inheritance. Still they can easily mate with other breeds of the same species. This also applies to wild animals, for example the wolfs living in the rainforest on the Canadian west coast prey on fish (and are maybe expected, with time, to go through a similar transformation as the predecessor to dolphins, that where actually wolf like animals, did when they resettled to the oceans) while inland wolfs prey on moose and elk etc, which requires completely different hunting technique, tactics, pack size and so on.

Are there any similar examples for humans? I reckon that living in the jungle or in the desert or on Greenland should reward different behaviours/traits that influence behaviour. Also going from a hunter-gatherer society to an agricultural society should reward different behaviours, social skills and similar aspect of human life.

Are humans like other animals in this respect (any examples?) or are we unique (?) in the animal kingdom when it comes to the influence of genetics on our behaviour?

One reason I ask is that I got second hand (without sources) information claiming that the natives of Mexico has the highest prevalence, of any population measured, of genes that are known to be connected with/causing ADHD. Mexico was also one the last places on the planet where humankind settled.

The argument went something like this: "during prehistoric time individuals with ADHD tendencies tended to be more adventurous than their peers and therefore traveled further". If this is true, people in Mexico's behaviour should be slightly different from people in current Kenya and Tanzania (by many scientists claimed to the birthplace of humankind), at least if you measure ADHD related traits.


2 Answers 2


I feel that 99% of the time that someone asks "are human unique concerning ?", the answer is nope. There's nothing exceptional about humans in this respect.

Rephrasing your question

Your question can be rephrased

Is heritability sometimes different from 0 or 1 for humans too?

If you do not understand well why this is a good rephrasing of your question, then you should definitely have a look at this post.

Is heritability sometimes different from 0 or 1 for humans too?

Yes, humans are not exceptional in this regard. In humans, other animals, plants, fungi, bacteria, archeabacteria and for any other living things, any behaviour (and any phenotypic trait in fact) can have a heritability that differs from both 0 and 1, or in other words, there can be for any trait both genetic and environmental variance underlying phenotypic variance in the population.

In fact, very few traits that have a non-zero genetic variance has no environmental variance. Have a look at the post List of heritability estimates in humans? for a list of traits on which we measured heritability.


The difficulty with a trait like ADHD is that the methodology to measure it vary a lot from one country to another or even from one practitioner to another. But yes, for ADHD too, there is both genetic and environmental variance underlying the observe phenotypic variance (Thapar et al., 2000).

  • $\begingroup$ FYI, @Remi.b, Chrome is flagging your website for not being secure. I would screenshot it to you except there is no capacity to post a screenshot in a comment. $\endgroup$
    – sterid
    Apr 9, 2018 at 3:05
  • $\begingroup$ FYI, my assumption was that humans are not unique in this respect. However, it is a very sensitive subject because a logical next step would be that certain ethnicities ("races") might be better on organizing their lifes or societies which would lead to the conclusion that different outcomes between ethnicities or countries are "fair" and well motivated. $\endgroup$
    – d-b
    Apr 9, 2018 at 8:43
  • $\begingroup$ Different ethnicities might differ for genetic reasons as much as they may differ for environmental reasons. The environment in which an individual is born will depends upon the climate, the social environment, etc... Environmental factors such as the social environment or the amount of wealth is greatly affected by the past events of the society in which the individual was born. There is nothing too sensitive about that. It becomes sensitive when you try to put a judgment of what is "good" or "bad" and when you try to make an a priori judgment of why the outcome is as it is. $\endgroup$
    – Remi.b
    Apr 9, 2018 at 16:28
  • $\begingroup$ For example, if you consider that the situation in Great Britain is bad because you don't like their food, then you might either not realize that food taste is very personal and you might put too a weird emphasis on food when judging the value of people. $\endgroup$
    – Remi.b
    Apr 9, 2018 at 16:28
  • $\begingroup$ As another example, if you consider that the current political situation in Syria is bad (which, so far the vast majority of people would happily agree with) and that you assume this bas situation is caused by the fact that they are genetically more violent, then you ignore the history of the region and the various international interest that is causing the current situation. That's were subject become sensitive. Anyway, I am definitely off-topic here! $\endgroup$
    – Remi.b
    Apr 9, 2018 at 16:28

As @Remi.b said (I upvoted, by the way), humans are rarely completely unique. The first law of behavioral genetics is that all behavioral traits show non-zero genetic influence (This is one of the most replicated findings in the field). More precisely, heritability estimates of behavioral traits are larger than zero, $h^2>0$ (but smaller than one, therefore environmental differences also contribute to the variance of the phenotype).

Population Differences

You say the following:

Different breeds of common domesticated animals such as horses and dogs clearly show different behaviour, instincts, social relationships and similar, due to their biological inheritance. Still they can easily mate with other breeds of the same species.

Then you question whether humans are different in this way. As you noted, it is a socially sensitive topic, but influential geneticist David Reich has very recently written an opinion piece on this sensitive topic (which I suggest you read in full, given your question).

For example, here is a quote by Reich:

While most people will agree that finding a genetic explanation for an elevated rate of disease is important, they often draw the line there. Finding genetic influences on a propensity for disease is one thing, they argue, but looking for such influences on behavior and cognition is another.

But whether we like it or not, that line has already been crossed. [...]

Regarding population differences:

And since all traits influenced by genetics are expected to differ across populations (because the frequencies of genetic variations are rarely exactly the same across populations), the genetic influences on behavior and cognition will differ across populations, too.

Attention deficit hyperactivity disorder

I have not looked into the genetics of ADHD. It is possible that native Mexicans have a higher rate of ADHD-increasing alleles -- I simply don't know. However, I would suggest you don't completely accept this claim without good sources from primary literature (Also the evolutionary "story" for this claim didn't sound too convincing, in my opinion. However, that may just be because you've been given a weak version of the argument). As with anything, the variance in ADHD is partially due to genetic differences.


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