How do humans evolve?

Human Genetics

Popular opinion in the world of science is starting to lean toward "yes," as scientists point to ongoing changes in our genes. For example, remember how we started keeping those domesticated animals? Well, until we starting milking one of those animals, adult humans didn't need to be able to digest lactose. However, over the past 3,000 years, more and more people's digestive systems have evolved to be able to handle milk [source: Shute].

Take natural selection out of the equation and think about how humans may have the possibility to drive their own evolutionary changes. About 20 years ago, doctors discovered a process called pre-implantation genetic diagnosis (PGD). During PGD, doctors can remove an embryo, test it for certain genes and then choose whether to put it back. First used as a way to reduce a child's chances of getting a genetic disorder, some parents are now taking advantage of it to choose the sex of their child. And think the old formula of getting genes from just two parents will always prevail? Maybe not. Since the late '90s, about 30 babies have been born with the genes of one father and two mothers after their mothers had material from a younger woman's eggs added to their own -- helping give their more mature eggs a better chance of leading to pregnancy [source: Shute].

Regardless of whether we are getting our genes from two or 50 people, what is going on within our genetic code and how we might be able to control it are only parts of the equation of modern-day evolution. We have cultural and societal norms, too, and this code of accepted behaviors is a big part of how we evolve.

For example, one shift in societal norms in many countries was giving women and people of color the right to vote. In that respect, we have evolved, although the right to vote is still threatened by political corruption, violence and human rights violations in nations around the world. We still have a long way to go.

Thanks to our access to instant information -- Internet, mass media -- our social ideals can go viral quickly. And where we can make accepted steps in positive directions, we also have the ability to go backward. Sometimes, though, the direction is debatable. In fact, consider this as you set off on your day: Has our evolution to being continuously online degraded our sense of community or further connected us to society and the world in which we live, work and play? Where will we go tomorrow? And what is our next evolutionary step?

Related HowStuffWorks Articles


  • Bloom, Paul. "How do morals change?" Nature. March 25, 2010. (July 12, 2010)
  • Ehrlich, Paul R., and Levin, Simon A. "The Evolution of Norms." PLoS Biology. June 14, 2005. (July 12, 2010)
  • Futuyma, Douglas. "Natural Selection: How Evolution Works." December 2004. (July 12, 2010)
  • Mayell, Hillary. "Oldest Human Fossils Identified." National Geographic. February 16, 2005. (July 13, 2010)
  • McAuliffe, Kathleen. 'They Don't Make Homo Sapiens Like They Used To." Disocver. February 9, 2009. (July 13, 2010)
  • Owen, James. "Future Humans: Four Ways We May, or May Not, Evolve." National Geographic. November 24, 2009. (July 12, 2010)
  • PBS. "Is Love in Our DNA?" (July 12, 2010)
  • PBS. "Where We Came From." (July 12, 2010)
  • Shreeve, Jamie. "Oldest Skeleton of Human Ancestor Found." National Geographic. October 1, 2009. (July 12, 2010)
  • Shute, Nancy. "Where Is Human Evolution Heading?" U.S. News & World Report. July 24, 2008. (July 12, 2010)
  • Smithsonian National Museum of Natural History. "Fact Sheet. David H. Koch Hall of Human Origins." March 17, 2010. (July 13, 2010)
  • Smithsonian National Museum of Natural History. "Homo sapiens." (July 13, 2010)
  • Smithsonian National Museum of Natural History. "Introduction to Human Evolution." (July 12, 2010)
  • Than, Ker. "'Key' Human Ancestor Found: Fossils Link Apes, First Humans?" April 8, 2010. (July 13, 2010)
  • Wade, Nicholas. "Still Evolving, Human Genes Tell New Story." The New York Times. March 7, 2006. (July 12, 2010)