Although, in humans, both males and females are selective in terms of whom they decide to mate with, as is seen in nature, females exhibit even more mate choice selection than males. However, relative to most other animals, female and male mating strategies are found to be more similar to one another than they are different. According to Bateman's principle of Lifespan Reproductive Success (LRS), human females display the least variance of the two sexes in their LRS due to their high obligatory parental investment, that is a nine-month gestational period, as well as lactation following birth in order to feed offspring so that their brain can grow to the required size.