August 13, 2017
Please share with Russell Bonduriansky
Dear Dr. Day,
I am most happy with Extended Heredity; of course, I knew much of what you review, but it’s swell to have so much in one place. I look forward to the time where extended heredity eclipses the Modern Synthesis. Let’s talk evolution:
I hold it axiomatic that competition is the rule in biology. Instead of selection going along a single dimension I think of a niche, where an animal can get food and shelter, there being a place in multi-dimensional space (at one dimension per hereditable characteristic) where the animal will be optimized for the niche. Of course, the distance from niche along your single dimension is the geometric sum of all those distances, but consider: as selection drives the animal toward the niche, the process is inefficient with each dimension potentially offering a temporary advantage with is neutral or maladaptive with regard to the niche. This changes dramatically upon niche-fall, as maintaining the place in space is a series of unambiguous opportunities and the inopportune.
The ensconced organism has the advantage, so selection is a competition. During some such process, each of perhaps 2 organisms is leaving its old niche for what may prove a better one … or perhaps a death trap, don’t you know. The form that undergoes speciation first may be able to hold onto the legacy niche while seizing the new. Thus, speciation is a contest in speed.
Of course, you already see where I am going with respect to extended heredity. That kind of mechanism is faster than old gene mutation and selection, so these mechanisms are truly the architects of change. Before you pack for Stockholm let’s run a number or two. Suppose speciation is going to take 2,000 generations; that means by old fashioned allopatric speciation, two chromosomes (I am limiting consideration to chromosomes, so bear with for a bit), 2,000 generations without consanguinity will kill the population.
Now let the population rise to 1,000. In the parental generation there are two sister chromosomes in two siblings. Assuming that the population is rigidly held at 1,000 and no chromosomes increase or decrease in frequency there are 2,000 homologous chromosomes and it will take 1,999 generations on average for the sisters to reunite.
Here I must scream for help. Should “average” mean median or mean? Is it really 1,999 or something more? It matters not; let the population rise to 2,000 or 10,000 and unquestionably sisters cannot significantly reunite before 2,000 generations of separation will render the offspring infertile.
Now nature takes the long view, and those thousands of generations will follow, bar extinction. But there is clearly a most powerful selective pressure for adopting a mechanism that maintains a population at some moderate size. The action of the mechanism has been described by a man named Sibly and the effect has been shown in humans, with no effect of education or income once kinship factors have been taken account of.
Playing around with fruit flies and doing some reading, I find that there are two mating strategies: love (based on kinship) and status (based on violence.) Quail, voles and fruit flies mate for love while mice and humans mate for status. Extinction follows the status stategy; I don’t know about the love strategy but I expect not. Looking at the Sibly curve it appears that any very large displacement from the equilibrium population size will drive the population to extinction. We are familiar with inbreeding depression; a man named Calhoun demonstrated outbreeding depression to the point of extinction and then promptly got forgotten. There is thus evidence (and there is a lot more) of mortal danger for humanity.
Further playing with my fruit flies has suggested that their outbreeding depression has pre-zygotic and post-zygotic mechanisms mediated by mismatch of arrays of methylation such that folic acid in clinically standard doses for women reduces fertility in my flies.
So here is my dare. Raise mice, at least eight lines of initially standard animals. Each generation pass four males and four females in each line on to start the new generation. Count pups over let’s say three or so days as they are born. Four lines get a diet of a blended 1,800 calorie well balanced diet for a woman only excluding any non-natural introduction of folic acid (yes, I know folic acid is not natural, but stay in focus) or other supplement. The other four lines get the same but each 1,800 calories’ worth gets 400 micrograms of folic acid from the grocery store blended in. (Don’t raise the mice in your bedroom; they can carry disease.)
I shall buy you a case of decent Scotch whisky if after 4 or 5 generations there is no significant difference in the number of mouse pups in the treated and untreated lines.
M. Linton Herbert MD