And most of that change has been genetic. In one study of a representative strain of turkeys, poultry researchers fed the same diet to turkeys from 2003 and to a control group of turkeys that were representative of that strain’s genetic pool from 1966. On average, the 2003 females grew to 33 pounds. Their 1966 cousins only got to 16.3 pounds.
The 2003 turkeys also grew much faster, reaching the same saleable weight twice as fast as their 1966 cousins. Even when they are raised under identical conditions, these are different animals with different genomes. Imagine if the average human were 300 pounds and reached what we now consider adult size at age 10, all while eating less food per pound of human. This is what just 60 years of scientific turkey breeding has wrought.