Evolution and speed

 Before the industrial and hygienic revolution, a woman gave birth to up to eight children. She started from an age like 16 years to up to 35 years. This high birth rate did not result in a significant population increase though. It took 2000 years to double the population. This implies that most babies and toddlers died before reaching puberty. Thus giving a significant evolutionary pressure to favour those who would not die from child deceases, poor hygiene and low quality food. Mathematically this implies that every 25 years a new generation evolved slightly better adapted to some specific traits making the chance of surviving young age greater. In hundred years, we have thus four generations, leading to 32 attempts resulting in eight lives. In 2000 years, the numbers become more impressive: 640 attempts leading to 160 adult lives. From the Roman era to now, you had 640 relatives out of which only 160 made it to you. The ancestry is however even vaguer. Here binary multiplications apply. You have two parents, out of four grandparents, carrying the genes of eight grand-grandparents. Presuming four generations per century, this makes for 2000 years, 2 power 80. This is an unpronounceable number: 1.208.925.819.614.629.174.706.176. A thousand years gives a more comprehensible number: 1 099 511 627 776. Still in the order of thousand billion ancestors. Sexual procreation allows therefore for very quick mixture of our 20.000 coding genes, which provided with pressure, such as child survival, leads to fast evolution for that specific trait. Billions of ancestors, potential help to create us over a thousand years, provided the relations are non-incestuous of course. For example, living in a predominantly dark climate with long winters, leads to skin colour adaptation, since vitamin D deficiency could lead to longer child diseases in winter. In malaria-infested regions, adaptations to blood cells Haemoglobin S evolved as adaptation for humans, as malaria is also a typical baby killer. Falling in love, often with a stranger rather than the girl or boy next door, assures that the genes of many remain tested, while populations in isolated areas such as islands or mountain valleys must consciously provide for fresh genes. Our urge for war, conquering and unrest when we are young might function as another guarantee to look for other genes. 

Modern society, fortunately, minimised the main cause of evolution, adaptation to the local climate and surroundings, being swamps, plains, mountains or islands, by minimising child death. In addition, we tend to live in the same comfortable houses and in cities in most high- and middle-income countries. Our evolutionary adaptations, such as a light skin in dark climates, small posture in mountains or the various types of noses and eye colours we developed all serve no purpose anymore. We are therefore a bit lost, we lack evolutionary pressure from children not reaching adult age, and we lack incentives for specific traits because we live in similar cityscapes. Very likely therefore is that our evolution comes to a standstill, next generations will be look alike of their parents. Unless the parents develop a preference for physical traits of a partner. Modern women tend to select high income, tall men, while men tend to select women with classical feminine traits such as large breasts and manicured fingers. Skin or hair colour seems hardly a selection criterion. Extrapolating one can thus expect ever-longer people with women with bigger breasts. However, these preferences lead only to changes in our appearance if the preferred couples make more children than the people not finding the physical fashionable partner. Therefore it remain likely that over 500 years humankind will mostly look like Brazilians, not because all populations mix thanks to international travel or migration, it will be because there are no drivers anymore for specific traits, and evolution will go slower due to decreased evolutionary pressure thanks to that we know how to keep a child alive.