Monday 30 June 2014

Population expanision in England with respect to mutation accumulation


When the Black Death (c 1380) halved the population of England, the deaths were disproportionately among the poorest (i.e. apparently 'eugenic').

Then the population took about 200 years (until around 1600) to recover (from 2-4 million) all the time under strong 'eugenic' selection (probably, nearly all of the surviving children came from the elite skilled craftsmen type working class and the 'intellectual' middle classes).

That is a 200 year doubling time. Then it took another 200 years for the population of England to double to 8 million (around 1800); then about 50 years to double again; and about 50 years to double again to 32 million after 1900; and then about 100 years for the most recent doubling.

So, 4 million was probably the usual maximum population for agrarian England, and there have been five doublings of population in about 600 years since the Black Death

(rounded numbers)

1350 - 4 million
1400 - 2 million
1600 - 4 million
1800 - 8 million
1850 - 16 million
1900 - 32 million
2014 - around 64 million

The rate of increase was slow and child mortality was very high until about 1800 or later - then three of the doublings have happened in 200 years since child mortality began to reduce, and fertility began to reduce, and selection was more and more strongly dysgenic.