The world’s population is growing, with some countries such as Brazil, the United States, and Australia expected to double their populations by 2050.
But what are some of the most popular hairstyles of all time?
It’s hard to pick out the trends, says Michael Greenfield, director of the research department at the Institute of Ageing.
“People tend to like different things and we tend to gravitate towards the trends,” he says.
He suggests some hairstyles may have evolved over centuries.
“We tend to see the hairstyles that are the most successful because they have been around for a long time,” he explains.
Some hairstyles have become more fashionable in recent years.
“For example, there is a lot of interest in the modern bob and the modern ponytail,” says Greenfield.
“There is a resurgence of the straight bob and there is also a resurgence in the straight ponytail.”
In the US, a new trend is for men to cut their hair short and tie it into a bun.
Another trend that has caught on is the rise of the Afro-American hairstyle.
“I think it is one of the more recognisable styles,” says Chris Williams, a hairstylist based in the US.
African American men have a long history of hairstyles with African roots, he says, and “a lot of these hairstyles seem to have a lot to do with that”.
“I think there is some connection to that, but I would be surprised if that is all it is.
We are very much in the era of hip hop, and there are lots of African American artists that have used that to their advantage,” says Williams.
However, he adds that there is “no denying that there are a lot more Afro American styles”.
Some men are opting for shorter haircuts, which can look better on a woman than a man.
In Brazil, a Brazilian men’s hair cut, called a duro, has become increasingly popular.
It’s shorter and more streamlined, which is a result of a history of being cut short by Brazilians, according to The Telegraph.
The hairstyle was popularised in the 1960s, when it was popular with the Brazilian military.
After the end of the Cold War, the country lost its independence, so it became a centre for hairstyle and body modification.
Brazilians began cutting their hair in the 1970s, and it’s now used by more than 50,000 men, according the Daily Mail.
Williams, however, says there is no denying the popularity of the style, which was popular among Brazilian soldiers during the 1980s.
A new trend of men going all-in on a short haircut has also emerged.
While the trend was initially popular in Japan, it has now spread to the United Kingdom and Australia, according TO.com.
Many hairstyles like the straight-line cut, which has a more defined look, have gained popularity in recent months.
One popular hairstyle is the long, loose-cut bob, which, with a short, straight bob, looks better on most women.
Men also like shorter hair, which are more manageable, according The Telegraph.
They are usually cut short to get the hairstyle to the perfect length, and often the men choose a hairstyle with a straight-point style instead of a straight line, which looks more like a ponytail, which most men would prefer, according The Telegraph’s hair expert, Dr Michael Green.
This trend is spreading to Australia, too, where a new haircut is also gaining popularity, according Toffee’s Hair.
Hair styles have changed since the 1930s.
“The men’s hairstyle has changed a lot since the beginning of the 20th century,” explains Dr Michael Goldstone, a professor of social and cultural anthropology at Melbourne University.
When the Victorian Government introduced the compulsory compulsory haircut, there was a perception that men were dressing down, he explains, and that women would take it upon themselves to help them look their best.
Today, there are more than 60 countries where the compulsory haircut is mandatory, with the United Nations saying in 2015 that more than a third of women globally wear a hair-straightening treatment, according International Business Times.
But not everyone is happy with the new trend, and some men say they don’t want to change their hair style.
Greenfield says that while he is a fan of the new hairstyle trend, he would not change it.
I think people should just go with what works for them,” he said.
As for the men who are going for the straight cut, Greenfield says it’s a natural evolution.
People tend not to change the way they look in a certain way, he continues.
So while the straight hair is a trend