About 200,000 years ago all humans were archaic bushmen, and given excellent nutrition in those days, these had an IQ around 67.
By 70,000 years ago, a few of the Bushmen had wandered out of Africa. Some of them wandered South towards India and Australia where they remained in warm environments and thus didn’t change much. A few headed North into the middle east. When the first winter hit; there was massive devastation as the bushmen struggled to adapt. 99% could not and in just a few months, the population dwindled down to almost zero. Only a few geniuses survived since they had the intelligence to make fire, sew boots, and build clothing and shelter. The children of these genius survivors of the first Middle-eastern winter were the first non-white caucasoids, and 70,000 years ago, these had an IQ of 77, which at the time, made them the smartest modern humans in the world.
A few of the non-white caucasoids tried to enter Europe where they were confronted by neanderthals. The non-white caucasoids were taller and faster than neanderthals, but scrawnier and weaker, so physically it was a wash. But neanderthals had the mental advantage, having had their wits sharpened by tens of thousands of years in Europe. Realizing they were no-match; the non-white caucasoids hid in the forests of Europe where they were exposed to even colder winters than they experienced in the middle east. By 50,000 years ago, they had evolved into the first whites, who at the time had a mean IQ of 86.
Packing an IQ of 86, they emerged from the forests of Europe ready to take on the neanderthals who also had a mean IQ of 86. But the whites had something the neanderthals lacked: language. The neanderthals were brutally slaughtered.
With their wits sharpened by killing off virtually all the neanderthals, about 30,000 years ago some of the whites had the confidence to enter the freezing Northeast Asia. Some of the brightest non-white caucasoids decided to join the trip too. When the caucasoids entered Northeast Asia, they were confronted by a blizzard so extreme, they couldn’t even see. Virtually everyone died except for a few geniuses who figured out how to adapt, as well as some caucasoids blessed with a rare skin mutation that protected their eyes from the blizzard. Since the geniuses and and the people with the skin protection were the only survivors, they mated and their children were the first Mongoloids. At the time these had an IQ of 92, making them at the time, the smartest people in the world.
By 10,000 years ago, the ice age began to recede. Thanks to the ice age, the mongoloids and caucasoids were now all smart enough to discover agriculture, however only the non-white caucasoids had both the brains and the fertile soil to make it happen. Once the non-white caucasoids invented agriculture, their population exploded and they suddenly produced freak high IQ mutations humanity had never before known. This raised their IQ by 13 points to 90, making them virtually tied with the mongoloids as the smartest people on Earth.
Packing an IQ of 90, they created the first civilization, and went around the world spreading agriculture. When the whites, mixed with the non-white caucasoids, they too inherited these new agriculture induced mutations, raising their IQs from 86 to 99. When the genes spread to East Asia, IQ jumped from 92 to 105; however the gene never spread all the way to the Americas, so those mongoloids stayed at 92.
When the genes spread to sub-Saharan Africa, average IQ jumped from 67 to 80, but some “black people” such as the capoids and the australoids, were too geographically remote to get the mutation, so these stayed around 70.
However ironically, just as the agriculture gene was making everyone 13 points smarter, agriculture itself was so unhealthy that brain size and complexity shrunk dramatically from malnutrition. Everyone who got the 13 point genetic boost also got hit by a 20 point decline caused by malnutrition.
However by the 20th century, nutrition had skyrocketed. Brains got bigger, people got taller, and those lost 20 IQ points came flowing back. This is known as the Flynn effect. However in the third world, nutrition still hasn’t come close to recovering.