This is less interesting than standard deviation, percentage living to 50/60/70/80, or life expectancy for men/women and at 1/5/18 years old though, as the issue here is it's hard to tell what is from things like dying in childbirth for both the child & mother and dying as a young child, vs being able to live longer, as we know people have lived well into their 80s and 90s since records began (ie Ancient Greece/Egypt/Sumeria) but this data implies that everyone used to die at 30, when in reality there were likely 2 peaks at 0-5 and 60-80
Life expectancy is how long you can expect to live from birth. It being 30 implies that you can expect to live 30 years, however in fact you'd most likely live <5 or >50 years