The pattern of human evolution in which the effects of natural selection are altered by cultural inventions. Culture can alter the direction of evolution by creating non-biological adaptations to environmental stresses (e.g., wearing insulating clothes on very cold days). This potentially reduces the need to evolve genetic responses to the stresses. This has meant that we have been able to remain essentially tropical animals biologically and live in colder regions of our planet. Biocultural evolution can also involve a mutual, interactive evolution of human biology and culture. An example of this has been the selection favoring sickle-cell trait in Africa. Human agricultural practices altered the environment, which resulted in factors that were advantageous to both the malarial microorganisms and the mosquitoes that transmit them between people. This, in turn, selected for the sickling allele.