North and South Koreans have grown so far apart during 70 years of separation that they share few common cultural traits and even look noticeably different.
Narrowing the wide sociocultural gap will be a prerequisite to reunification, because such sharp differences in thinking and lifestyles would make it virtually impossible for the two people to live under one government. The cost of bringing them together is likely to skyrocket.
One NGO worker aiding North Korea said, "North and South Korea have been separated for 70 years and things are now completely different in the North and South."
Even laughter is different. Kim Chol-jin (35), who defected to South Korea two years ago, said, "I still don't get the jokes when I watch [a famous TV comedy program]. I've shown North Korean comedy to my friends at work and they just looked puzzled."
People from the two sides also look different. According to a study by Mitsuhiko Kimura at Aoyama Gakuin University in Japan, the average height of a North Korean male in his 20s in 1940 was 163.4 cm, taller than his South Korean counterpart who stood 162.3 cm tall. But in 2010, the average height of the South Korean male was 174.2 cm compared to 165.4 cm in the North.
South Koreans also live longer, with the average life span 13-20 years longer than that of North Koreans.
An even bigger problem is ways of thinking and values are changing. For instance, North Koreans are brainwashed since kindergarten to worship nation founder Kim Il-sung and his heirs.
Traditional customs have also changed. In North Korea, the biggest holidays are Kim Il-sung's birthday on April 15 and Kim Jong-il's birthday on Feb. 16. New Year's Day for North Koreans is just an ordinary day that marks the start of a new year.
South Koreans eat songpyeon or crescent-shaped rice cakes during the Chuseok thanksgiving holidays, but North Koreans eat them on New Year's Day.
Years of fuel shortages have virtually paralyzed railway transport in North Korea so people there do not travel en masse to their home towns during traditional holidays as South Koreans do.
An aid worker who visited North Korea around 30 times since 1994 said, "I was surprised to see how male-dominated North Korean society is. Women are discriminated against in the North due to the strange combination of Confucianism and communism."
North and South Koreans differ in the way they spend their free time. Farmers in agricultural cooperatives in the North rest once every 10 days.
On their days off, North Koreans like to play cards but do not go out to eat or head to the countryside like South Koreans do.
Marriage customs, too, are different. In North Korea, brides wear hanbok or traditional Korean dress and hold the weddings in the groom's home. When the ceremony is over, North Korean newlyweds pay homage at the statues of Kim Il-sung and Kim Jong-il and have their photos taken there. There are no honeymoons.
In the South, the dead are usually cremated, but North Koreans prefer burial.
An aid worker said, "When I go to North Korea, I realize that the only thing I have in common with people there is the language, but I wonder if we really are the same people. We need to re-establish common ground before the division becomes permanent."