A more widely accepted theory is that, when human ancestors moved from the cool shady forests into the savannah, they developed a new method of thermoregulation. Losing all that fur made it possible for hominins to hunt during the day in the hot grasslands without overheating.
Humans are the only primate species that has mostly naked skin. Loss of fur was an adaptation to changing environmental conditions that forced our ancestors to travel longer distances for food and water. Analyses of fossils and genes hint at when this transformation occurred.
Stephen Wooding, calculate that the last sweep probably occurred 1.2 million years ago, when the human population consisted of a mere 14,000 breeding individuals. In other words, humans have been hairless at least since this time, and maybe for much longer.
Hair loss was also presumably aided by technological innovations such as clothes, fire and cave-dwelling, which lessened the importance of fur for keeping warm at night. Head hair, meanwhile, became thicker and more luxuriant, protecting our ancestors' brains from the midday sun, and also retaining heat in the cold.
They found that humans seemed to have the genes for a full coat of body hair, but our genome regulation currently stops them from being expressed. They also found that when a species loses hair, they do it by changes to the same set of genes repeatedly, and uncovered several new genes involved in this process.
A more widely accepted theory is that, when human ancestors moved from the cool shady forests into the savannah, they developed a new method of thermoregulation. Losing all that fur made it possible for hominins to hunt during the day in the hot grasslands without overheating.
Darwin suggested it was due to sexual selection, that our ancestors preferred less-hairy mates. Others have argued fur loss helped deter hair-dwelling parasites like lice. But the majority of researchers today posit that reduced body hair had to do with thermoregulation — specifically, with keeping cool.
Broadly speaking, evolution simply means the gradual change in the genetics of a population over time. From that standpoint, human beings are constantly evolving and will continue to do so long as we continue to successfully reproduce.
As we age, our prolonged exposure to testosterone starts to play a visible role on other body hair as well. Just like it transforms the vellus hair on a young man's face into a thick beard, it also changes the nearly invisible hair that grows in places like our ears into thicker strands.
Hair that is tightly coiled offers the best protection against the sun's potentially damaging rays, which could explain why this trait evolved in early humans in Africa and straighter hair emerged as some humans moved into cooler areas.
We will likely live longer and become taller, as well as more lightly built. We'll probably be less aggressive and more agreeable, but have smaller brains. A bit like a golden retriever, we'll be friendly and jolly, but maybe not that interesting. At least, that's one possible future.
“It means modern humans probably started wearing clothes on a regular basis to keep warm when they were first exposed to Ice Age conditions.”
Humans diverged from apes [specifically, the chimpanzee lineage (Pan)] at some point between ~9.3 million and ~6.5 million years ago (Ma), and habitual bipedalism evolved early in hominins (accompanied by enhanced manipulation and, later on, cognition).
More reproduction followed, and more mistakes, the process repeating over billions of generations. Finally, Homo sapiens appeared. But we aren't the end of that story. Evolution won't stop with us, and we might even be evolving faster than ever.
Much later, when they evolved into primates, their tails helped them stay balanced as they raced from branch to branch through Eocene jungles. But then, roughly 25 million years ago, the tails disappeared. Charles Darwin first recognized this change in our ancient anatomy.
Humans now evolve faster than ever, and it's not because of genes. At the mercy of natural selection since the dawn of life, our ancestors adapted, mated and died, passing on tiny genetic mutations that eventually made humans what we are today.
During menopause, a woman's body stops circulating estrogen but continues to circulate the same amounts of testosterone. The imbalance of hormones causes the appearance of some male secondary sex characteristics, like coarse facial hair. You should let your doctor know if your facial and body hairs are growing quickly.
Like so many things, it comes down to a mixture of genetics and hormones. We know that at least some of the genes for hairiness are carried on the X chromosome – and the way these genes are expressed varies between different men and ethnic groups – but hairiness also correlates with high testosterone levels.
Testosterone is accumulated over a lifetime and levels continue to rise unopposed to estrogen levels with age. The testosterone acts on hair follicles in the ear, as well as other areas such as the nose. The follicles then become primed to grow more thick hair as a result.
The model, called Mindy, provides a terrifying glimpse at what people could look like in 800 years if our love of technology continues. According to the company, humans in the year 3000 could have a hunched back, wide neck, clawed hand from texting and a second set of eyelids.
In 100 years, the world's population will probably be around 10 – 12 billion people, the rainforests will be largely cleared and the world would not be or look peaceful. We would have a shortage of resources such as water, food and habitation which would lead to conflicts and wars.
While, as shown with creatures such as hydra and Planarian worms, it is indeed possible for a creature to be biologically immortal, these are animals which are physiologically very different from humans, and it is not known if something comparable will ever be possible for humans.
Caucasians have the highest hair density among the ethnicities studied. Black people have the lowest. Asian people have hair density that falls somewhere in between.
Even though they grew up with the Internet and find it nearly impossible to separate from their connected devices, millennials are just as likely to experience hair loss – both from hereditary factors such as male pattern baldness, and from environmental factors such as stress and poor diet.
The short answer is we have evolved to have nails because they help us pick things up (like food), pick things off (like bugs), and hold tightly onto things. Early humans who had these type of nails (instead of claws) tended to live long enough to have babies and pass on the fingernails gene to their kids.