With regards extraterrestrial aliens, I’ve heard Neil deGrasse Tyson say on several occasions, that even though there is a high degree of DNA similarity between humans and chimps (estimated at 98.8%), that the 2% accounts for the vast difference in technology of them fishing ants out of nests with a stick and our putting a man on the moon [his larger point being if aliens were only 2 % smarter than us, we probably couldn’t understand them or fathom their technology].
Is this a valid comparison? Didn’t Neanderthals (for example) has the same number of chromosomes as us? And is DNA alone an indicator of (potential) intelligence? Final question, how far back does our current DNA structure go?
The process of going from DNA to phenotype is extremely non-linear. The fact that our total difference in DNA is 2% does not limit the difference in intelligence to only 2%. For comparison, chimpanzees are more than 2% stronger than our species, and we can run more than 2% farther than chimps.
And while DNA puts limits on the phenotype, the environment can affect development, including gene expression. Environment ranging from in-utero conditions, to nutrition, to sensory stimulus.
Doesn’t that 1.2% differance (from my calculation of the number you provided) does a lot more than just determine how smart you are, it sets up an totally differnt architecture that allows for more advanced learning. It also detemines that you get less hair, differnt eyebrows and other stuff that has nothing to do with intelligence.
According to this study, environment plays a large factor when you’re young, but as you age the genetic factor becomes more prominent.
For the Chinese reared-apart twins, the study found that their IQ scores became more similar over time. The intraclass correlation for their IQ scores increased from 0.51 at the first testing (Time 1) to 0.81 at the second testing (Time 2), indicating a strong genetic influence. Additionally, the within-pair difference in IQ scores decreased from an average of 11.93 points at Time 1 to 7.93 points at Time 2. This convergence suggests that as these twins aged, their shared genetic makeup played a more prominent role in determining their intelligence, despite being raised in different environments.
Similarly, the Danish adult reared-apart twins also showed an increase in IQ similarity over time, with their intraclass correlation rising from 0.64 at Time 1 to 0.74 at Time 2. This pattern further supports the notion that genetic factors become more influential in shaping intelligence as individuals grow older. The Danish twins also exhibited a slight but significant increase in their mean IQ scores from Time 1 to Time 2, highlighting the stability of intelligence over time in adults.
Yes, I think so. But (if my understanding is correct) Neanderthals had the same amount of chromosomes (and DNA?) and though intelligent, didn’t invent complex machinery.
That 2% (or whatever) difference figure is pretty much useless. It is a popular factoid that doesn’t actually tell you much. Let’s say you have a two different printings of a book, each 100 pages, each with 100 words per page. The two books are 2% different. You can get that by 98 pages being absolutely identical between them and 2 pages completely different, you can get that by every single page having 2 different words on it, and you can get somewhere in between where some pages are identical and some have 10 different words.
DNA is the same way: human and chimp DNA can be 98% identical and still have every single gene be different.
They may not have had speech, which can be a limiting factor in innovation, or maybe their idea of a good/valuable time didn’t involve inventing complex machinery. They were also considerably more pacific than the hominids who provided much of our DNA (though we have some of theirs due to interbreeding).
DNA accounts for a great deal of it, but nutrition, environment and health also factor significantly as well.
To give an example, North and South Korean people are extremely similar, genetically, yet due to decades of malnutrition - especially being starved of nutrition during the vital age of 0-10 when the brain needs it the most - the average North Korean probably has significantly lower IQ than the average South Korean.
But yes, in terms of species vs species - humans vs chimps - there can be little doubt that our difference in brains/brain structure makes all the difference.
It’s not even clear what a “2% difference in intelligence” would even mean. No method of measuring intelligence can actually quantify it numerically. The best we can do is (sometimes) say things like “this person is smarter than that person”, and thus produce a ranking, and say things like “this person is smarter than 73% of the people in the population as a whole”.
As for Neanderthals, the primary reason they never developed our level of technology is that they’re all dead. We killed them. How it came to be that we were the ones who won the genocide isn’t known, but it probably wasn’t intelligence. As I understand it, where Neanderthal and sapiens relics are found from near the same time and place, they also have similar levels of technology, and their brains were actually a bit larger than ours. One hypothesis is that we won the genocide simply by virtue of being more aggressive than them. Another is that it was just pure luck.
Compared with chimps, meanwhile, the absolute most significant difference is that we have language, while they don’t (they do have communication, but at a level much simpler than language). In a species with language, when one member discovers some useful new trick, others learn it, and soon everyone knows how to do it. Which paves the way for other useful tricks that weren’t possible before, and so on, and so technology grows exponentially. In a species without language, though, even if they’re just as good at discovering clever tricks, all those tricks get lost when their discoverer dies.
DNA alone isn’t a predictor of intelligence, and certainly counting the percentage similarity isn’t enough to give you any kind of meaningful read.
It’s better phrased to say that your DNA helps an organism meet the preconditions for intelligence (big brain, toolmaking, etc), but at some point the brain is too complex to take any single gene and boil it down to “the intelligence gene”.
Supposedly the Neanderthals were deficient in a few genes for speech, so they might have had the capacity for intelligence. But without being able to talk about it, they wouldn’t have been able to share it, and wouldn’t have been able to use it very well. They might have done better in the modern world where we know how to handle neurodiversity better, whereas in the past we just probably killed them all for being too different.
The number of chromosomes is mostly irrelevant - dozens of mammals and other animals, even plants, have more chromosomes - and even the number of genes is mostly irrelevant - again, many other animals have far more. What matters is what the genes do, how they are expressed, the proteins they make. Very small changes appear to have massive lasting effects.
Pretty sure the gene differences are not spread like that though. We do have a lot of genes in common; a quick googling suggests it might be closer to 99% for protein coding genes.
The key thing for the OP is that 2% DNA difference doesn’t automatically map to 2% physical difference. A small number of genes may just code for “make the cortex much bigger” and result in an organism that is light years ahead in abstract thought and planning.
The locations where mutations happen should be random. So except in cases where there is strong selective pressure against it, they should be spread everywhere. Especially for codons (Wordle word!) that are synonyms that would not change gene expression but would count in the difference.
Humans have around 175 mutations per generation
The last common ancestor of humans and chimps was around 6 million years ago. Call a generation 20 years, that’s 300,000 generations. Time enough for more than 50,000,000 mutations to accumulate. They’re gonna be spread far and wide.
In humans (probably other species, too), the reason that intelligence differs between individuals is probably 50-80% due to genetic variation, and the rest due to random environmental effects.
Between different species, the difference is probably 100% due to genetic differences. Humans are much smarter than chimps, because of differences in DNA between the two species.
This doesn’t necessarily mean different genes, especially in closely related species like primates, but different alleles for those genes. For example, there was recently news about the human variation of the NOVA1 gene being important in language development. In that case it was a single amino acid change that is only in the human version of the gene which creates the language ability change.