He pointed out the huge host of health problems that came with agriculture: hard labor; poor quality food; diseases from living densely.
Life expectancy dropped from the adoption of agriculture until well into the industrial revolution, with the adoption of public health.
based on what data exactly?
This is as expected, because they had switched from a diet where the main sources of proteins and fat were of animal origin to one where the main sources of proteins and fat were plant seeds.
They did not have our modern knowledge about essential nutrients, so at least in the beginning they had not been able to choose a balanced diet.
It appears that they have eventually accumulated enough experience to improve their food habits (after some centuries). Since the beginnings of agriculture, the cereals have always been the cheapest source of food, but in time it has been learned that they are not enough so they have been then combined with legumes (e.g. lentils, peas and faba beans) and with oily seeds rich in essential fatty acids (e.g. flax seeds).