score:4
The two are unrelated, and any "resemblance" between the two ages is coincidental.
If the "life expectancy" was 35, it would be a weighted average of the ages of people who died in childhood, and people who lived to be adults, and who could expect to live a normal lifespan approaching 70, from Biblical times, (at least for men; women often died in childbirth). That is, the deaths would be "bi modal," from ages 0-5, then again around ages 65-70. The life expectancy in your chart rose over time when as the left "mode" diminished in size. It is NOT a bell curve with a peak around age 35.
As for the rise to the Presidency, the U.S. Constitution mandates that no one be elected to Congress before the age of 25, to the Senate before the age of 30, and the Presidency before the age of 35. Assuming a "wunderkind" was elected to Congress at age 25-26, s/he should serve at least 2-3 terms (4-6 years) in Congress before running for Senate. That person would be expected to serve, if not a whole Senate term of 6 years, at least 4-5 before running for President. Or possibly have an equivalent career track outside of government.
There has been a school of thought that people, particularly men, are not fully adult and mature until age 25. Lower thresholds for adulthood at 21 or 18 only signify "more adult than not."
Ironically, Joe Biden was among the youngest elected Senators (barely 30 on inauguration day), but did not become a viable candidate for President until his old age.
Upvote:7
The other answers touch on this point, but I think it needs to be emphasized: The quote in the question demonstrates a gross misunderstanding of the concept of average life expectancy.
Overall average life expectancy is less meaningful than average life expectancy at a given age. The average life expectancy at birth was much lower than it is today, but that was mostly because of the high rate of fatal childhood illnesses. If you made it to age 10, you were mostly in the clear. Children who died were replaced, and there was no shortage of old people. Modern medicine has only increased the average life expectancy of an adult by about five years.
Upvote:18
The Wikipedia article about life expectancy incudes the following:
Life expectancy increases with age as the individual survives the higher mortality rates associated with childhood. For instance, the table above listed the life expectancy at birth among 13th-century English nobles at 30. Having survived until the age of 21, a male member of the English aristocracy in this period could expect to live:
- 1200–1300: to age 64
- 1300–1400: to age 45 (because of the bubonic plague)
- 1400–1500: to age 69
- 1500–1550: to age 71
So Americans in the 18thC who survived to 35 look likely to have had a reasonable chance of surviving several Presidential terms, at least.