I have been debating the following topic with a friend.

  • She argues that humans do not descend from chimpanzees or orang-utans, because if we did, such animals would share the same cognitive thinking that humans have.
  • I argue that we do descend from that such animals, and that a high protein diet has allowed early humans to develop a better memory, intelligence, and other mental processes.


  • What is the the real origin of human intelligence?
  • If non-human animals do have intelligence too, why is their intelligence not as advanced as humans?
  • 2
    $\begingroup$ This question appears to be off-topic because it is much more about how evolution works than cognitive science. Perhaps the biology SE would be a better venue? $\endgroup$
    – Krysta
    Commented Jul 30, 2013 at 17:39
  • $\begingroup$ probably. Thanks for the advice $\endgroup$
    – Eric Frick
    Commented Jul 30, 2013 at 17:43
  • $\begingroup$ I have heard some explanations revolving around the standing position and opposing thumb, leading to the gripping hand, tool use and ultimately higher cognitive functions. No matter the merits of this theory, ultimately, it does not seem directly relevant to establishing a link between primates. Following your friend's logic, why would any animal on earth not be a human? Why would chimpanzees or for that matter turtles, frogs or insects not benefit from increased memory or intelligence? $\endgroup$
    – Gala
    Commented Jul 30, 2013 at 18:06
  • 3
    $\begingroup$ @Krysta I would think the evolution of cognitive function to be completely on topic. $\endgroup$
    – Gala
    Commented Jul 30, 2013 at 18:15
  • 2
    $\begingroup$ Also, I didn't feel it necessary to point this out earlier but this isn't really an all or nothing proposition. Animals obviously have some information processing capacity, memory, intelligence, etc. $\endgroup$
    – Gala
    Commented Jul 30, 2013 at 19:11

3 Answers 3


If non-human animals do have intelligence too, why is their intelligence not as advanced as humans?

Notions like “advanced” or “better” really have no place in evolutionary thinking. Again, evolutionary fitness is about self-reproduction and success compared to whatever competition is present at any moment. There is no force “optimizing” species to meet some external criteria of “progress”.

One important observation is that (relatively) simple species have in fact been quite successful (in terms of number of individuals, total biomass, capacity to survive climate changes and other disruptive events, etc.). Humans have been flourishing very recently (few thousands of years), colonizing big parts of the earth, reaching large population numbers but before that there is evidence that they went through a severe population bottleneck as recently as 70000 years ago. Great apes populations are also not very large and all species are considered endangered.

Sustaining a large brain and human intelligence is in fact extremely onerous. The human brain requires a lot of energy. Furthermore, it has become too big to go through the mother's womb so that it still undergoes growth after birth, meaning that human babies require a lot of care and protection. All that suggest that “high intelligence” is not always such a big advantage, evolutionary speaking. As often, there are trade-offs and various successful “strategies”.

In any case, you might be interested in Wikipedia's article on the “Evolution of human intelligence”.

  • $\begingroup$ I signed up just to have the pleasure of up voting your answer. I think the bottleneck was for Cro-magnon in eastern south of Africa, while Neandertal came to Europe 200.000 years ago. But we are supposed to be much more Cro-magnons than Neandertals. My own belief regarding intelligence and empathy is that it emerged because modeling the world and other beings helped both predators and preys ... at high processing cost. It is however surprising that diminishing returns did not stop intelligence growth. Almost did. $\endgroup$
    – babou
    Commented Sep 5, 2013 at 22:36

Let's first be clear that we didn't evolve from monkeys/apes/etc. That's a common misconception. Evolution states that we and monkeys/apes/etc. evolved from a common ancestor. Same with fish. If you go back far enough, we and fish share a common ancestor... we did not, however, evolve from today's Salmon or Macaque.

That being said, the origin of intelligence is an elusive topic. Intelligence isn't the most tangible concept to study in an evolutionary context as the associated molecular evidence is highly circumstantial. For example, it's difficult to interpret what behavioral differences emerged from the differences in receptor distribution and types associated with our genetic fission from the common ancestor.

Now that we've said that, there's several theories; many of them stem from language. It is thought that the articulation allowed by language allows us to more carefully think about things... but there's always the possibility that the reasoning came first and facilitated the language.

One of the more interesting theories I've read is the bicameral mind. Of course, note the criticisms against it:

"It is one of those books that is either complete rubbish or a work of consummate genius, nothing in between! Probably the former, but I'm hedging my bets." -Richard Dawkins

Others argue that human consciousness is a social construct.

  • $\begingroup$ Good point in the first paragraph but I don't think the evolution of intelligence has much to do with evolutionary psychology. One of its main assumption/tenet/characteristic is that specific behaviors or psychological traits evolved. That's the main point of contention and the level evolutionary psychologists discuss; they don't have much use or much to say about some general information processing capacity. Furthermore, evolutionary thinking about cognition is certainly not limited to evolutionary psychology, there is no reason to consider it “belongs” to its proponents in any way. $\endgroup$
    – Gala
    Commented Jul 31, 2013 at 5:23
  • $\begingroup$ the question has been changed since I answered it, from human reasoning (a process with an associated verb: to reason) to human intelligence (a much broader concept). I don't equate "general information processing" to either human intelligence or human reasoning. Even inanimate objects can process information. $\endgroup$ Commented Jul 31, 2013 at 12:37
  • $\begingroup$ Also, I don't think insects "reason". They certainly process information... whether they're intelligent or not depends on how you define intelligence (different researchers will define it different ways, but there's a lot of room for anthropomorphizing there.) $\endgroup$ Commented Jul 31, 2013 at 12:42
  • $\begingroup$ I see your point but it is only tangentially related to the one I was trying to make, I still don't think any of this has much to do with evolutionary psychology. $\endgroup$
    – Gala
    Commented Jul 31, 2013 at 13:24
  • $\begingroup$ I think that's a debate in itself, but since it's not a primary point, I will just remove it to avoid the distraction. $\endgroup$ Commented Jul 31, 2013 at 13:29

Your own theory is bad because it seems to follow from a Lamarkian interpretation of evolutionary theory. In Lamarck's idea, a crab's offspring will have the genes bigger claws if the crab exercises his own claws a lot before giving birth. In the same way, you're suggesting that the way ancient human diets improve their mental health somehow led to this mental health being passed down to us.

To better understand the question, you should think not about what habits ontogentically lead to better thinking, but about what problems that ancient humans uniquely faced such that ultimately only those with our intelligence were able to successfully mate and reproduce.

  • $\begingroup$ +1 Good points even if I am not sure if the problem in the OP's thinking is specifically related to the inheritance of acquired characteristics. As an aside, it's true that this view has been associated with Lamarck's name but in fact his ideas were much broader than that and this particular mistake was also committed by Darwin (e.g. in The Expression of the Emotions in Man and Animals). Besides neither of them had any notion of “gene”, for obvious reasons. $\endgroup$
    – Gala
    Commented Aug 4, 2013 at 8:53
  • $\begingroup$ Good answer. But why does certain humans (those ones that later did reproduce and successfully mate) actually developed intelligence or cognitive thinking? That's my main question and the whole debate about $\endgroup$
    – Eric Frick
    Commented Aug 16, 2013 at 18:35

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