I have just come across another contribution to this topic, thanks to the Economix blog.
Carl Haub of the Population Reference Bureau presents estimates which suggest that about 5.8 percent of all people ever born are alive today. I have been looking to see how these compare with those which Roger Thatcher presented to the British Association for the Advancement of Science in 1984. There are differences, but we are basically in the same ballpark.
What has been especially intriguing however has been the comparison between the Haub approach, which looks at birth rates, & the Thatcher approach which concentrates on mortality. Of course a great deal of speculating is needed for both.
We are told that birth rates (per 1000 population of all ages) have fallen steadily & consistently since the birth of agriculture around 8000 BC, and at 23 per 1000 are now less than a third of what they were then. Mortality rates on the other hand appear to have remained at a constant level of 35 (per 1000 population of all ages) for most of the last 2 millennia, almost up to the beginning of the C20th. Since then they have fallen precipitately, so that they are now less than a quarter of the level of 8000 BC. And still, we are told, falling rapidly – longevity is increasing at a rate of about 5 hours per day.
At the start of the C20th the population of the world still numbered less than 2 billion. It has now passed 6 billion. But these figures make it more startlingly clear that it is not the birth rate which is responsible. Have we any right to tell others to stop reproducing, just so we can live longer & consume the world’s resources for ourselves? Or to take a greater share of the productive capacity of the young to provide for the kind of care & support we need when elderly, infirm or demented?
What will be the effect on human evolution of limiting reproduction to a simple two-will-do replication of each mating pair?
The age structure of population varies between countries, so even with constant fertility rates, the birth rates will be higher in those countries which have higher proportions of young people today. We will need population movement to balance out these imbalances, to provide the care we need.
Carl Haub of the Population Reference Bureau presents estimates which suggest that about 5.8 percent of all people ever born are alive today. I have been looking to see how these compare with those which Roger Thatcher presented to the British Association for the Advancement of Science in 1984. There are differences, but we are basically in the same ballpark.
What has been especially intriguing however has been the comparison between the Haub approach, which looks at birth rates, & the Thatcher approach which concentrates on mortality. Of course a great deal of speculating is needed for both.
We are told that birth rates (per 1000 population of all ages) have fallen steadily & consistently since the birth of agriculture around 8000 BC, and at 23 per 1000 are now less than a third of what they were then. Mortality rates on the other hand appear to have remained at a constant level of 35 (per 1000 population of all ages) for most of the last 2 millennia, almost up to the beginning of the C20th. Since then they have fallen precipitately, so that they are now less than a quarter of the level of 8000 BC. And still, we are told, falling rapidly – longevity is increasing at a rate of about 5 hours per day.
At the start of the C20th the population of the world still numbered less than 2 billion. It has now passed 6 billion. But these figures make it more startlingly clear that it is not the birth rate which is responsible. Have we any right to tell others to stop reproducing, just so we can live longer & consume the world’s resources for ourselves? Or to take a greater share of the productive capacity of the young to provide for the kind of care & support we need when elderly, infirm or demented?
What will be the effect on human evolution of limiting reproduction to a simple two-will-do replication of each mating pair?
The age structure of population varies between countries, so even with constant fertility rates, the birth rates will be higher in those countries which have higher proportions of young people today. We will need population movement to balance out these imbalances, to provide the care we need.
Another intriguing question which has ocurred to me: although it is not true that the living outnumber the dead, is it possible that the total years of life of those people now living exceeds the total number of human life years of the past?
And there can, after all, be no evolution without death.
And there can, after all, be no evolution without death.
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