Evolution is fundamentally a change in the frequency of gene variants, known as alleles, within a population over successive generations. This ongoing process does not require dramatic physical transformation, only that some heritable traits become more or less common over time. The question of whether humans are still evolving is easily answered: yes, the process is continuous and unavoidable. Modern life, technology, and medicine have not ended human evolution, but have instead altered the environment, thereby changing the direction and pace of selection pressures. The vast human population ensures that the raw material for change is constantly produced, and the environment is always shifting.
The Ongoing Processes of Genetic Change
The engines of evolution—mutation, genetic drift, and natural selection—remain fully operational within the human gene pool. Mutation provides the constant influx of new genetic variations upon which all other processes act. The human germline mutation rate is estimated to be approximately 1.16 x 10^-8 mutations per base pair per generation, which translates to roughly 60 to 100 new single-nucleotide mutations in every individual born today.
Genetic drift, which is the random fluctuation of allele frequencies due to chance events, is also an active force. While its effect is reduced in the current massive global population, it remains significant in smaller, more isolated local groups or in cases of population bottlenecks. Modern human migration patterns and historical founder effects continue to shape local genetic landscapes through this random process.
Natural selection, the non-random survival and reproduction of individuals with advantageous traits, continues to respond to the modern environment. New selective pressures emerge from highly processed diets, exposure to synthetic chemicals, and increased population density. These factors create novel challenges that favor certain genetic profiles, ensuring that the human genome remains under constant pressure to adapt.
Observable Evidence of Recent Evolution
Concrete evidence demonstrates that human evolution has been rapid and pervasive over the last 10,000 years, particularly following the advent of agriculture. The most celebrated example is lactase persistence, the ability to digest the sugar in milk into adulthood. This trait is genetically controlled and spread rapidly in populations that adopted dairy farming. The ability to use milk as a nutrient source provided a significant survival advantage, leading to the convergent evolution of at least five different genetic variants for lactase persistence across different dairying populations.
Adaptation to extreme environments also provides clear recent evidence of evolution. Populations living on the Tibetan Plateau have evolved a unique genetic profile to cope with low-oxygen conditions. The EPAS1 gene, found in high frequency in Tibetans, prevents the overproduction of red blood cells, a dangerous condition common in unadapted lowlanders. This advantageous gene variant spread dramatically within the last few thousand years and may have been acquired through interbreeding with the extinct Denisovans.
Infectious diseases remain one of the strongest selective forces acting on humans today. Malaria resistance has driven some of the fastest recent evolutionary changes in the human genome. The spread of the sickle cell trait, caused by a mutation in the HBB gene, is a classic example of an allele providing resistance to malaria. More recent examples, such as a gene variant that protects against Plasmodium vivax malaria, have been observed to surge in frequency in populations over short time spans.
How Modern Life Shapes Our Genetics
Modern technological and cultural changes have profoundly influenced the direction of human evolution by altering the environment and survival criteria. Medical intervention does not stop evolution; rather, it changes the parameters of selection. By transforming conditions that were once lethal, medicine allows individuals with previously deleterious gene variants to survive past reproductive age and pass those genes on.
Global migration and increased gene flow are homogenizing the human gene pool, mixing populations that were once genetically isolated. This extensive intermingling introduces new genetic variability, which can accelerate the spread of beneficial traits but also increases the frequency of rare, previously localized variants. The massive increase in the global human population also means that there are more opportunities for new mutations to arise and spread.
Modern life has introduced new forms of selection, such as changes in reproductive timing. Studies of contemporary populations have identified subtle selection pressures favoring genes associated with traits like a lower risk of Alzheimer’s disease or a reduced propensity for heavy smoking. These traits correlate with a longer lifespan and reproductive window, confirming that human evolution is a continuously unfolding story.