Would unintelligent humanoids end up losing their language and inventive powers?

Question

If a hominid with a human-like mind became less intelligent due to adaptation to a reduction in food, would this be likely to lead to the loss of language and the ability to make complex tools?

Answer 1

Zeiss' answer seems to be a perfectly correct answer to your question, because we just don't really know. In contrast, it is completely unsuitable for the purpose for which the question was most likely asked. Therefore, I will try to answer differently.

Starting with definition:

Natural selection is one mechanism of biological evolution that leads to directed changes in populations that increase their average adaptation, or adaptation to environmental conditions. The measure of success in natural selection is fitness. It can be considered at the level of individuals or individual genes. Organisms with advantageous traits are more likely to survive and reproduce, leading to an increased frequency of advantageous genes in the population.

Consider an environment with limited access to food. (As an aside, it is also important how limited the resources will be in this environment). With a limited amount of food, one would expect a correspondingly large reduction in population, as is often seen in natural processes of animal population regulation rather than a significant reduction in energy (food) requirements.

So in such an environment, will natural selection promote individuals that need less food, or rather those that will be able to obtain significantly more food than other individuals of the species or than other species competing for the same food?

In all likelihood, human (or human-like) brain capacity is a trait that significantly helps adaptation to an environment with reduced food supply, so on a general level one might expect that natural selection is unlikely to promote individuals with much weaker intelligence, although it is possible that other traits such as speed, agility or reflex might be even more important and promoted.

There may, of course, be combinations of adverse environmental conditions that will actively promote individuals with less intellectual abilities. I can quickly think of some kind of radiation that increases the risk of brain cancer in young (adolescent) individuals with higher brain activity, or some kind of brain parasite that is more likely to attack such individuals. But these, in turn, are factors that intelligent populations, at the appropriate level of development of civilization (such as humans more or less since the nineteenth or twentieth century) would be able to cope with. So the occurrence of such factors would have to be preceded by the collapse of civilization or would be important in species that have not yet developed a technical civilization. So this kind of situation is rather unlikely and even if such combination of conditions happens, it will not be caused only by limited resources (or strictly reduced food supply). It seems to me that there is a much higher probability of the complete extinction of a humanoid species due to extremely unfavorable environmental conditions than the emergence of such conditions that will result in the survival of the species but with significantly reduced intellectual abilities.

To summarize my answer. I consider extremely unlikely the occurrence of such environmental changes that would cause a significant reduction in humanoid intelligence, one that would lead to the disappearance of language or tool-making skills, although of course it is not impossible.

Answer 2

The simple answer here is, we don't really know.

There is speculation that this is more or less what happened to Homo Floresiensis ("Hobbits" of Flores Island), who had significantly smaller brains than modern humans as well as being under four feet tall -- but so far, we have so little evidence beyond their mere existence, we don't even know if their smaller brains actually made them less intelligent, or if so, whether they were enough less intelligent to lose some of the mental abilities we normally associate with human populations.

The link between brain size and intelligence itself is a bit shaky, based on my reading; at least one of our ancestor species (Neanderthal) had slightly larger brains, on average, than we do, yet they're gone and only their genes remain, bred into our own lines.

Yes, a big brain needs lots of energy to operate, as well as having very important nutritional requirements for development (adequate fat and protein in the diet, for instance). What happens over evolutionary time if those needs aren't met, we don't know. Does a population get smaller and less smart, or do they just die out?

If you pay attention to anthropology research, you'll know as soon as I do.