Intelligence and Sexual Selection

In a previous post, the traditional or usual explanation of the rise of intelligence in evolution was questioned. That usual explanation is that the grasping hand came first, then tool use, then intelligence in general. Maybe it was a little of one, a little of another, then a little of the third and round and round until there was some sort of stopping place for all three together, which was humans, either like us or one of our predecessors. This is all very convenient for ease in understanding, and buttresses any thoughts we might have about the dominant position of tool use, which is simply the very first step in technology, in determining society. Technological determinism is the name given to the idea that technology determines culture, but this goes further. It says technology determines evolution, at least during this phase of the rise to intelligence.

Paleontologists have discovered various fossilized skeletons which show the correlation between brain size, which somehow is related to intelligence, and other skeletal parts such as the hand, upright posture, jaw shape, and some other things. But we all know that correlation is not causality. If we are looking for a determinant of whether exo-planets that originate life will also originate intelligence, we need causality. So the initial concept of hand to tools to thought is used to denote that causality, but there is no way to prove or disprove it.

One means of proof is to show that there are no other alternatives, the proof by elimination method. But, since alternatives simply consist of other pathways being thought of and discussed, it is easy to come up with them. The previous post mentioned talked about how altruism, group living, individual recognition, observation of medicinal effects, and observation of discrepancies in behavior and other attributes, together with brain asymmetry in use but symmetry in development, when all added up together form another discussable pathway. Each of these is a short evolutionary step and all are reasonable changes, motivated by things other than the development of intelligence in general.

In this explanation, tool use did not happen and then cause intelligence, either in one step or in a gradual feedback loop. Instead, something else caused intelligence, and then tool use arose from it. It postulates a one way street from intelligence happening, as determined by brain size, neural density, convolutions of the brain, and all the other physiological correlates of intelligence, and then tool use flowing from the available computational power of the improved brain.

What else other than tool use or nutritional and medicinal use could possibly cause the brain in a species to improve in its ability to compute and figure out things? It might be nice to generate a list of all the things that a primate or alien equivalent might do that would be benefited by having a better brain. Two already listed are altruism within a small group of genetically similar animals and ability to discriminate between foodstuffs for nutritional and medicinal contributions. Another one which was downplayed was communication ability. This certainly is concentrated on one side of the brain, so it invokes the brain asymmetry/symmetry argument. It was downplayed in other posts in favor of tool use, but perhaps it is time to rethink that argument.

Besides staying alive, and perhaps more important that staying alive for a long time, is the ability to procreate. The quantitative benefit of some genetic advantage arising from a mutation is the average number of gene copies that arise from the advantage, as compared to the pre-mutation number. Does communication play a role in procreation?

In tribal units such as polygynous gorillas, where there is a dominant male, it might not. There, as in many other animals, strength and ability to combat plays the biggest role. In monogamous species, it might play some role, in that if sexual selection was based on communication ability to a degree, it would be favored. In promiscuous species, it might play an even larger role. Here, communication should be thought of as not just vocal communication, but also posturing, gesturing, posing, grimacing and anything else that involved sensory exchanges between a male and a female of the species.

Courtship displays are common in species here on Earth. They occur in species of many phyla and include both behavior and physical attributes in the lower species. If communication through the many means possible was one of the observables used in the choice of a male by a female, then communication would be a trait that was also selected by evolution. The brain of males in that species would grow to enable the communication skills that were needed to ensure mating occurred and procreation was successful. If these communication skills involved voice communication, speaking or singing, that would be enhanced; if they involved gesturing or touching or posing, those parts of the brain connected with dexterous motor skills would be enhanced; if they involved facial expressions, that part, and so on.

Some of these skills, particularly those involved with motion, or even eye-hand coordination, or tactile feedback, or other associated skills, would also play a role in facilitating tool use. Once they had been improved to some degree, they would be available for application to finding or using existing physical objects for tools, and then to modifying what was found. The other side of this coin is that, in addition to genetic changes, being involved in a courtship display might lead to some learning at a deep level, on how to use the hand to perform some particular motions, and that learning might be translatable to similar motions needed to fashion a tool or to use it for some purpose. The learning and the genetic changes might be symbiotic as well, as a gene which enables a primate or alien equivalent to learn how to manipulate objects in different ways, via analogous use in courtship displays, would be positively reinforced. The learning might be wholly done in successive attempts at courtship displays, but still be useful for tool making and use.

In short, there is a third pathway to the development of intelligence in certain types of animals that can be considered, which would not violate any paleontological insights. This pathway has a very different causality chain than either the first, tool use directly, or the second, nutritional and medicinal use, and it might have different conditions or requirements. One check to keep in mind when contemplating alternative pathways is that on Earth, no other species developed the kind of tool-using intelligence that one species of primates did. If other species have the same type of activities in conjunction with these pathways but did not develop tool use, then a reason for this would have to be developed.