Question

can you assign a half-life to a population of human? e.g.can you find a group of 1000 people born in 2000, and note that 500 of them are still alive in 2050, and thereby deduce that 260 of them will be alive in 2100? explain the difference between the death rates of people and the death rates of radioactive atoms.

Answer 1

No! We cant assign such a half-life time for human population.

Note that the reason why we can do it radioactive nuclei is that their rate of decay is proportional to the number of nuclei present at any given instance of time. When we write this condition mathematically and solve the resulting equations, it turns out that their number will be halved after each interval of fixed length which we call half-life.

We cant obviously do this for humans as the death rate of humans is not directly proportional to the number of people present in given sample. For example if we consider that the average human life span is 70 years, then very few will die in the initial phase say till 40-50 years and very few will live up to say 90-100 years. Maximum deaths will occur between span of say 60-80. This is very different from the behavior of the radioactive nuclei which decay at very fast rate initially and the rate continuously decreases as their number decreases. So we cant assign such half life to human population.