In most mammalian populations, the sex ratio at birth is often balanced or slightly weighted toward females due to a variety of factors, such as natural selection and parental investment strategies. As these populations age, a shift can occur where older age groups might have a higher proportion of males.
This phenomenon is largely attributed to the fact that females generally have a higher life expectancy compared to males. Consequently, younger age groups may have a balanced or slightly higher number of females, but as age increases and mortality rates among males and females start to differ, the proportion of males in the population can increase.
Therefore, considering this biological and demographic context, the statement "In most mammalian populations, the sex ratio is often weighted toward females, but the population shifts toward males in older age groups" is:
True
