The Gene: An Intimate History by Siddhartha Mukherjee
Notes from The Gene.
There is no such thing as perfection, only the relentless thirsty matching of an organism to its environment. That is the engine that drives evolution.
To explain the intersection of genetics, natural section and evolution, Dobzhansky resurrected two important words -- genotype and phenotype. A genotype is an organism's genetic composition. It can refer to one gene, a configuration of genes, or even an entire genome. A phenotype in contrast, refers to an organism's physical or biological attributes and characteristics - the color of an eye, the shape of a wing, or resistance to hot or cold temperatures.
A gene determines a physical feature - by generalizing that idea across multiple genes and multiple features.
In humans, a mutant BRCA1 gene increases the risk for breast cancer- but not all women carrying the BRCA1 mutation develop cancer. …trigger-dependent or chance-dependent genes are described as having partial or incomplete "penetrance" - i.e., even if the gene is inherited, its capacity to penetrate into an actual attribute is not absolute. Or a gene may have variable "expressivity" - i.e., even if the gene is inherited, the extent of it becoming actualized into an attribute varies from one individual to another. One woman with the BRCA1 mutation might develop an aggressive, metastatic variant of breast cancer at age thirty. Another woman with the same mutation might develop an indolent variant; and yet another might not develop breast cancer at all…
Genotype + Environment + Triggers + Chance = Phenotype
The process of selection, notably, acts on a physical or biological attribute - and the underlying genes are selected passively as a result. A misshapen nose by a bad day in the ring - i.e. nothing to do with genes (chance) - but if mating contest is judged only by the symmetry of noses, then the bearer of the wrong kind of nose will be eliminated.
Phenotype drags genotypes behind it like a cart pulling a horse.
On intelligence testing:
…the concept of IQ is powerfully self-reinforcing: it measures a quality imbued with enormous meaning and value whose job it is to propagate itself. The circle of its logic is perfectly closed and impenetrable. Yet the actual configuration of the test is relatively arbitrary. You do not render the world intelligence meaningless by shifting the balance in a test - from visuospatial perception to short-term recall, say - but you do shift the black-white IQ score discrepancy. And therein lies the rub. The tricky thing about the notion of "g" is that it pretends to be a biological quality that is measurable and heritable, while it is actually strongly determined by cultural priorities.
It is - to simplify it somewhat - the most dangerous of all things: a meme masquerading as a gene.
Genes cannot tell us how to categorize or comprehend human diversity; environments can, cultures can, geographies can, histories can. When genetic variation is statistically the most common, we call it normal - a word that implies not just superior statistical representation but qualitative or even more superiority. When the variation is rare, it is termed a mutant - a word that implies not just statical uncommonness, but qualitative inferiority, or even moral repugnance.
And so it goes, interposing linguistic discrimination on genetic variation, mixing biology and desire. When a gene variant reduces an organism's fitness in a particular environment - a hairless man in Antarctica - we call the phenomena genetic illness. When the same variant increases fitness in a different environment, we call the organism genetically enhanced. The synthesis or evolutionary biology and genetics reminds us that these judgments are meaningless: enhancement or illness are words that measure the fitness of a particular genotype to a particular environment; if you alter the environment, the words can even reverse their meaning.
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