Human Intelligence Comes from the Genes

LAMC3 Gene and Effect on Brain Convolutions
The difference between the brain on the left above and the brain on the right, comes from a single gene -- LAMC3 -- which influences the formation of convolutions in the cerebral cortex. Brain convolutions allow for much greater volume of cerebral cortex, which is associated with the higher intelligence seen in apes, cetaceans, and humans (one of the apes). An alteration of the nucleic acid sequence in the LAMC3 gene in humans can apparently lead to the loss of convolutions in the cortex in affected individuals, as seen in the image above.

The folding of the brain is seen only in mammals with larger brains, such as dolphins and apes, and is most pronounced in humans. These fissures expand the surface area of the cerebral cortex and allow for complex thought and reasoning without taking up more space in the skull. Such foldings aren't seen in mammals such as rodents or other animals. Despite the importance of these foldings, no one has been able to explain how the brain manages to create them. The LAMC3 gene – involved in cell adhesion that plays a key role in embryonic development – may be crucial to the process.

An analysis of the gene shows that it is expressed during the embryonic period that is vital to the formation of dendrites, which form synapses or connections between brain cells. "Although the same gene is present in lower organisms with smooth brains such as mice, somehow over time, it has evolved to gain novel functions that are fundamental for human occipital cortex formation and its mutation leads to the loss of surface convolutions, a hallmark of the human brain," Gunel said. _Medicalxpress

Thousands of genes take part in the intricate developmental dance of forming the central nervous system in all its complexity. But specific genes play more dominant roles in differentiating human brains from brains of "lower" animals.

Genes control the size of particular systems and components of the brain which are instrumental in providing for more rapid mental processing and more complex processing. Some brains can hold more ideas in the mind simultaneously, while performing transformative operations on those ideas. "Human calculators" capable of computing solutions to complex arithmetical and mathematical problems in their heads, are one obvious example. But the mental machinations of scientific theorists, elite diagnosticians, and top level novelists, illustrate the same type of differentiation of mental ability -- largely originating at the genetic level.

James Watson -- one of the discoverers of the modern genetic theory of DNA inheritance -- received almost universal condemnation for expressing a few elementary facts of human genetic biodiversity. Here is some background information concerning that shameful episode of modern human culture and its prejudices:

GNXP: James Watson tells the Inconvenient Truth

Slate: Created Equal [AF Note: After being threatened with a similar fate as that of Watson, the much beaten-down Saletan (author of the slate piece above) published a "mea culpa" and submitted to the PC inquisition]

Useful PDF article from Robert Plomin discussing Genes and Intelligence

It is critical to understand how many genes are involved in weaving the fabric of higher intelligence. It is not a question of finding THE GENE for intelligence. Rather it is a question of understanding how all the many genes which create the potential for intelligence, work together.

And it is important to become a bit more sophisticated about how a crucial variability in gene expression can occur -- even when conventional genetic analyses fail to distinguish between two genomes.

Humans are not all the same. In fact, no two humans are exactly the same -- even identical twins. This is true for reasons of gene expression, in all its many levels of complexity -- both known and unknown. These differences can also originate from differences in experience and culture, as in when identical twins are separated at birth and raised in entirely different environments. But even then, the powerful impact of genes on the life outcome of the separated twins is all to obvious.

IQ is not everything. Executive Function (EF) is also crucial to life success. But EF is perhaps even more heritable than IQ. That is why it is so crucial to take advantage of a child's critical developmental windows for boosting the components of competent thinking, acting, and planning when one can. After that time period passes, it is mostly too late for those at the greatest genetic disadvantage.