Evolution is a continuous process. A common misconception is that humans are somehow 'fully evolved' and our genetic make up is now fixed. This could not be further from the truth since selective pressure is still exerted on humans.
Future human evolution will continue gradually as it has done in the past. However two major factors that have emerged recently (in evolutionary timescales) combine to make the future evolution of humans significantly different to the past evolution of humans. These are the use of medical technology and the individual lifestyle choices that people living in a significant proportion of the world are able to make.
Medical technology is now used to keep individuals alive who would have died in the past without such intervention. The death of individuals before they are able to produce viable offspring is a powerful evolutionary force. The use of medical technology therefore allows individuals to survive and reproduce who are, or have at some time been, reliant on the existence of that technology. This raises the spectre that humans may evolve to have a symbiotic relationship with their own technology.
Lifestyle choices individuals make on family size are significant evolutionary forces. The genes of individuals who choose not to have any children will not be passed on to the next generation. The genes of people who choose to have a single child late in life will not be passed on very effectively to the next generation. However, the genes of people who have many children with a number of partners will have their genes well represented in the next generation.
Potential Future Human Evolutionary Characteristics
The average human brood size is currently one. That is to say that each birth usually produces one baby. The worldwide trend towards mothers having fewer maternities means that those that give birth to twins or even triplets may have more children in total than those who have singleton births. Medical technology now means that whilst twin and triplet maternities are usually much shorter and the babies much smaller, they now usually produce more viable children than singleton births. It has been postulated that this mechanism will continually increase the human brood size until there is some form of intervention.
Many future adaptations will be caused by the absence of a selective pressure. For instance myopia could become much more common because myopic individuals can now survive and reproduce successfully, where in the past they might not have been able to.
In general the human genome will become ever more diverse as the diversity of individuals that are able to survive and have children increases.
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