There are all sorts of television shows and movies about the next human evolutionary step and they typically involve the emergence of paranormal abilities. However, the reality is that nearly all evolution involves movement along dimensions that already exist within the species. For example, when we look at our immediate evolutionary precursor, H. erectus, we see that they had an average cranial capacity of about 1,000 cm³. This is significantly more than the 600 cm³ capacity of its predecessor H. habilis but much less than the modern human capacity of 1,350 cm³.
In fact, if we were to project a successor to H. sapiens, we would first imagine that it would have an average cranial capacity in the range of 1,700 cm³. Such people should exist within the human population at the rate of one in 4,300. In fact, they are much more common than that. A preliminary analysis suggests that the 'fat tail' of cranial capacity matches the fat tail of ratio IQ. In other words, cranial voumes of 1,700 cm³ are found in one in 260 individuals.
Clearly, the supposition is, as is the case in Physical Anthropology, that larger brains will lead to greater intelligence and essentially new intellectual abilities. We accept that H. erectus was smarter than H. habilis and that H. sapiens is smarter than H. erectus and that cranial capacity is evidence of that. However, we resist the notion that larger brains in modern humans result in higher intelligence despite the anthropological tradition that militates for the relationship.
Also, and this is critical, the notion that one form of homo directly supplants the other is incorrect. H. habilis lived from 2.3 to 1.4 million years ago. Its successor, H. erectus, lived from 1.8 million to 300 thousand years ago. For 400 thousand years both were extant. Its successor H. sapiens (including archaic forms) lived from about 600 thousand years ago to the present. So, H. Erectus and H. sapiens were simultaneously extant for about 300 thousand years. For at least 100ky, H. sapiens, H.neanderthalensis coexisted in the Levant. A successor species to H. sapiens, what I call H. macrocephalus or big headed man, could co-exist with it for quite some time, at least in theory.
We actually have good evidence that sympatric speciation is already creating H. macrocephalus. It shows up first in our efforts to measure the intelligence of children. IQ was originally a ratio, Mental Age/Chronological Age X 100. In other words a 150 IQ eight year old will perform on an IQ test in a similar way to a normal twelve year old. When these tests were first developed it was found that the standard deviation was about 16 points. In other words, there should be no children with IQs over 200 and only about one in three million should have IQs over 180.
However, extraordinary IQ turned out to be much more common than predicted. 180 IQ children turned up at the rate of about one in thirty thousand or one hundred times more often than they should. 200 IQ children, instead of being non-existent, were found at the rate of about one in five hundred thousand. In reality, there were quite a few children who were so smart that, statistically speaking, they should not have existed.
Spearheaded by David Wechsler, this anomaly was simply eliminated by edict. He argued that mental age lost its meaning in adults. People typically reach intellectual maturity at age 16. There was no way, he argued, to prove that the excess high IQ people found would retain the same ratio superiority in adulthood. With the Wechsler IQ test and now with essentially all IQ tests, scores are rendered as a 15 point standard deviation that is forced to conform to the normal distribution. In other words, now there are no 200 IQ people and 180 IQ people are found one in three million.
Of course, these very high, anomalous IQs would need to correspond to some actual intellectual performance difference and preferably different in kind rather than degree. Oddly, David Wechsler said, 'The genius (as regards intellectual ability) not only has an IQ of say 50 points more than the average person, but in virtue of this difference acquires seemingly new aspects (potentialities) or characteristics. These seemingly new aspects or characteristics, in their totality, are what go to make up the 'qualitative' difference between them."
When one questions the members of ultra high IQ societies, they often talk about a qualitative difference in intellectual processes and often mention 150 or so IQ as a line of demarcation between 'regular' people and themselves. D.K. Simonton stated, "Even if the exceptionally bright individuals are able to target their use of language to the needs of their audience, the complexity of their ideas may be less accessible to listeners with IQs more than one standard deviation lower than their own."
In other words, there is a preponderance of evidence that the very high IQ people are not simply doing the same problem solving, just faster and more accurately, but rather are actually doing something different. This qualitatively different intellectual activity is precisely what we would expect if we are talking about a different kind of species. I, myself, have often been mystified that lines of reasoning that are absolutely compelling to me seem to elude those around me.
Now, we know that greater cranial capacity doesn't necessarily mean more intelligence. There are factors of brain morphology and differences in neurotransmitters, etc. That is why, when looking in the normal +/- 2 σ range, the correlation between intelligence and cranial capacity is weak. However, what happens when we look in the range of 160 D15IQ?
Before we start, I will give a very short lesson in statistics. Suppose that there is no correlation between IQ and cranial capacity. Then, if a person has an D15IQ of 160, what is their likely cranial capacity? It is 1,350cm³ just like everyone else. Suppose that we find that they have a cranial capacity of 1,750 cm³ or about +4σ. What is the probability that it is a random variation? It is about 0.003%. In other words we can be quite confident from just a single data point that at the extremes IQ and cranial capacity are highly correlated.
Suppose we find two people, selected at random, from the population of 160+ D15IQ and both have cranial capacity of over 1,750 cm³. The probability that there is no statistical significance to this is 0.003%² or 0.00000009% or effectively zero. Because of this and because I happen to know quite a few people with IQs over 160, I decided to find out if high IQ and large cranial capacity are correlated.
My brain capacity is 2007 cm³ or well above the 1750 cm³ criterion. I have a friend who is known for having one of the highest IQs on record. I asked him to take a measurement, too. His result was 1986 cm³. Because of a height adjustment, (+/- 2 cm³/cm) his adjusted cranial capacity is actually very slightly more than mine. I received two other submissions from people with 160+ D15IQs and cranial volumes of 1,936 cm³ and 1,700 cm³. Because all were male, I used the mean of 1,406 cm³ and a standard deviation of 109 cm².
Even though the sample is quite small, the fit is so good that it has a very high statistical significance. Furthermore, I received measurements from people with IQs below 160 but still very high. From a metastudy of IQ/cranial volume databases I was able to perform a linear regression and determine that 'Cranial Capacity' IQ fits the line IQ=.2×V- 181. With adjustment, for example, my IQ calculates to about 215. What we find is that the linear regression fits ratio IQs! In other words, it appears that David Wechsler was wrong. The fat tail is valid and ratio IQs probably are a better measure of intellectual distance.
From this, we find that the IQ of a person with a 1,750 cm³ cranial volume is 169 R16IQ. This is an equivalent of 153 D15IQ. From this, we can estimate that H. macrocephalus comprises about 0.04% of the population. While this is a very small percentage, it still represents about 2,800,000 people. So, the population exists and it appears that they differ qualitatively, not just quantitatively, in their cognitive abilities. However, are they engaging in assortative mating behavior that would support the theory of sympatric speciation?
Anyone who is familiar with high IQ societies knows that they represent a hotbed of assortative mating. The reason for this is obvious upon reflection. The intimate relationship of pair bonding requires a high degree of mutual understanding. Research has, not surprisingly, found that the correlation of spousal IQ is substantially higher than for other personality traits. Additionally, as IQ increases, its significance in the search for a mate increases.
Suppose we set a reasonable limit that IQ should be within 20 points in order to have an acceptable degree of mutual understanding in mates. For a person with an IQ of 100, that means that the population of acceptable mates will be from 80 to 120 IQ. In other words, 80% of the population will have acceptable IQs. However, for the 130 IQ person, their range of acceptable IQ is 110 to 150. This reduces the mating pool to just 25% of the population. However, for our typical H. macrocephalus, the acceptable range is 133 to 173. Now the mating pool has been reduced to less than 2% of the population.
Clearly, for this population, finding a mate with an acceptable IQ becomes the single biggest challenge in their mate selection. Especially, over the last 50 years with the emergence of high IQ societies and the Internet, the tools for the exceptionally high IQ people to find one another for the purposes of mating have improved. While no strong research has verified it, the evidence would suggest that the 153 D15IQ (s.d. 3.5) population is now a semi-isolated breeding population.
It is less than clear when, precisely, a population becomes a new species. Clearly, if mating between two populations results in no offspring or no fertile offspring, the populations are clearly separate species. However, in cases where fertile offspring result but the reproductive rate is below replacement, we have two species de facto if not de jure. It is only a matter of time before they will, through genetic drift, become reproductively separate. In the case of sympatric speciation there is an extended period of time when the two populations in theory could re-integrate. However, by behavior, they will not and, as such, they comprise a nascent species.
While cranial capacity has been a hallmark of species classification in hominims, post cranial characteristics are also important. I suspect that we will find traits such as a continued trend toward neoteny, gracility and longer lifespans to be likely differences. We are seeing some evidence from the initial group suggesting these traits.
The four cases also all exhibited very significant brachycephaly which is likely an adaptation to the difficulty of birthing a head of large cross-sectional area. The more circular the head the less circumference for a given cross-sectional area.
Two of the four have noted very low basal body temperature. This makes sense in that a normal sized brain consumes about 20% of the calories. A brain 30% larger would consume 26% of the body's calories. Lowering the prevailing body temperature, by cooling the blood, will assist in heat transfer.
Because we are looking at the extreme, four examples is actually sufficient to establish the statistical validity of the IQ/brain size correlation. While not part of our circle, the very high IQ Chris Langan has commented on his enormous head, stating that it is over 3 standard deviations above the norm. The purpose of further research would be to determine any other traits common to the group and to measure the degree of assortative mating within the population.
The research, I believe, would be worthwhile and, with research assistants, I would undertake funding and executing the research. The newly formed experiment.com may be able to fund this research.
An approximate estimate of ratio IQ from 15 point deviation IQ can be calculated by subtracting the deviation IQ from 128, multiplying the remainder by 1.8 and then adding back 128. So, the TNS requirement of 148 is (148-128)x1.8+128=164. This is approximately equivalent to the IQ that Cox, et alia estimated for Darwin, Locke, Bayle, Hegel, etc. According to that set of estimates, it probably represents the floor for historical science and philosophical genius.