Considering that life expectancy for a 30 year old man is around 79.3 in Germany 2018, and you're reading it to be 76.9 in 1930, that's far less change than I have ever heard anyone previously suggest.

First, 2.4 years on average is significant. Second, the scholarly average is for people who were on average 54 when appointed to their position. That means there is no childhood mortality or deaths below that age to bring the average down.

Also medieval and a Renaissance scholars were by definition more “elite” than the average European of the day - it would make sense to compare their lifespan to those of similar socio-economic status today.

In many cities you can see that the lifespan increases with the average household income of the neighbourhood, and if you look at say, Monaco, one of the richest per-capita cities, the average life expectancy is 85 for men and 93 for women, over 20 years longer than the average European scholar.

Erasmus of Rotterdam was one of the greatest scholars of the Renaissance and certainly one of, if not the, best Latinist. His father was a priest, and so could not legally marry Erasmus' mother, who was apparently the father's housekeeper; they were not well-off. The parents died from the plague in 1483, and Erasmus was thereafter raised and educated by monks, whom he eventually joined out of poverty. He went on to become one of the most influential Latinists in history. There was a nobility during the Renaissance, but underneath that was a churning sea of social mobility that rewarded intelligence and capability.

How exactly this contradicts relationship between social class and lifespan?

There have been gains but one has to see it in the context of health life expectancy which in the UK currently is about 63 years.

Modern medicine helps to extend life expectancy but often those last 10+ years are miserable clinging to life whereas in the past once you got, for example, a chronic heart disease you would not survive very long. The healthy life expectancy in the past can only be a guess but probably not that considerably lower for certain classes.

The parent mentions the obviously dramatic impact of infant / child mortality rates. That would definitely apply to the 59 average you're referring to, it's a huge factor in that average.

An intentionally simple example of how dramatic it is:

Ten people, with 20% of them dying in childhood. Then reduce that to just one dying in childhood.

80, 75, 70, 65, 65, 60, 50, 40, 2, 1 = 50.8 avg

Now drop the childhood deaths down to just one.

80, 75, 70, 65, 65, 60, 60, 50, 40, 1 = 56.6

You gained 5.8 years on life expectancy from cutting the rate in half. Now take us from 1650 childhood mortality rates, to affluent modern nations where it's eg 5 deaths per 1000 live births in a nation like Canada (and that's down by 75% from 20 per 1000, 50 years ago). I can only imagine how high the rate was 400 years ago, it would absolutely tank the average in an epic way.

Am I totally misunderstanding the study? Wouldn't this figures be only people who were scholars appointed on adulthood? That would exclude children.

I suppose that hinges on whether the parent was opening a broad point about life expectancy from the topic, or only talking about the adult scholars. I'm not sure which they intended, I was guessing based on their phrasing that they were targeting the broader notion of how it's commonly perceived that life expectancy has increased over that time.

Bill Gates for example routinely claims in interviews / discussions that there has been a massive gain in life expectancy (technically correct) and he'll claim that broadly (mostly false), dropping context on the fact that it's heavily caused by childhood mortality figures plunging. I've seen him do that numerous times over the years (usually he gets agitated when someone challenges him, moves into sarcastic mode, and points out the huge gains for the average person on life expectancy, which is partially bunk). It's a common point of intellectual dishonesty in the scientific & health establishment, because they want to pretend the life expectancy gains for adults have been far greater than they really have been (for their own self-interested reasons). I suspected the parent comment was riffing on that aspect, where it's a pushed point of quasi propaganda that life expectancy has soared for everyone.

From this paper that is specifically looking at scholars: "Fifth, because the scholars were not appointed until they reached young adulthood, our investigation was limited to adult mortality. The effects of shifts in infant and child mortality on the evolution of life expectancy were neglected."