For example, our average height dropped 5 inches when we switched to agriculture. Our average life span dropped too.Do you have something to back those assertions up? Height & longevity are generally related to childhood nutrition.
Regarding average height, this article from Scientific American (
http://www.scientificamerican.com/article.cfm?id=why-are-we-getting-taller) states "...over the last 150 years the average height of people in industrialized nations has increased approximately 10 centimeters (about four inches)" and "...examinations of skeletons show no significant differences in height from the stone age through the early 1800s. " The article also points out that the probable reason for the increase in height over the past 150 years is most likely related to improvements in nutrition. This article (
http://www.livestrong.com/article/542877-the-average-height-of-humans-over-time/) discusses a 3" loss of height after the Middle Ages, but again relates that to changes in nutrition.
On longevity, this article (
http://www.livescience.com/10569-human-lifespans-constant-2-000-years.html) notes that the Greeks and Romans who survived childhood were also living into their 70s.
