But many people questioned the couple’s parenting skills, saying they should not have taken a toddler on such long journeys.

“Simba’s mother and I thought carefully about that before we took him to the Arctic at the end of 2014,” Xu said. “Firstly, both of us are diehard travel enthusiasts and we don’t want to give up our dream of travelling around the globe for the sake of caring for our kid. Secondly, for a kid, being several years old is the most important stage to develop his cognition of the world. Most kids will learn about this world and learn words through cartoon books or television, but we think it’s better for our son to touch this beautiful planet with his hands and see it with his eyes.

“Those beautiful experiences will be buried like seeds in his mind and will blossom and bear fruit as he grows up.”

Xu, originally from Liaoning, is a partner in a kayak club on the shore of scenic Qiandao Lake in Zhejiang’s Chunan county. He said he preferred to spend his savings on global travel, rather than property.

“The tour to the Arctic cost us 300,000 yuan (US$45,400) and the trip to the Antarctic 600,000 yuan.

That’s perhaps the price of a toilet in Shanghai or Beijing,” he said. “We don’t buy expensive houses and we don’t think money is that important. What we care about is that parents accompany their kid to play around; otherwise he’ll grow up soon and you will miss those particular, precious moments.”

He said Simba, who was born in May 2012, did not feel exhausted on their journeys and was happy every day – happier than his parents.

“We didn’t rush the journey and adopted a slow pace of travelling so the kid can still have enough rest during the journey,” Xu said. “He was excited by what he ate, what he played, and what he saw every day was different.”

Xu was previously a hiking guide in Tibet and Xinjiang. He met his wife, a former engineer in Shanghai, while travelling. They gave their son the nickname Simba – after the main character in the hit Disney film The Lion King – because he was conceived in Africa.

When he was 18 months old, his parents took him to row a boat on the Irtysh River in northern Xinjiang. Although it was chilly, Simba enjoyed playing with stones, picking up leaves and chasing swans.

“I realised my son liked playing in the wild,” Xu said. “I was glad to see that, as there is a popular saying that nature is the best teacher in the world.”

The family came up with the idea of going to the Arctic after Simba kept saying he wanted to see a real polar bear after seeing pictures of one in a cartoon book when he was two.

The family travelled through 12 countries in 185 days on their three-wheeled motorcycle, starting in November 2014. But after a week in the Russian Arctic they had not encountered a single bear and Simba was disappointed.

Xu was not surprised by the lack of bears and put on a white bear costume to cheer his son up. “Simba’s eyes lit up and he yelled, ‘I must tell Dad I saw a polar bear’,” Xu said.

In November last year, the family started their 146-day tour to South America and the Antarctic.

Xu said Simba had developed a sense of environmentalism after being exposed a lot in the wild and often interacting with animals.

One day in the Antarctic, Simba drew penguins on a sheet of paper and asked Xu to write “wildlife is our friend” beside them.

“He told me to take a picture of him showing this paper and to upload the picture on the internet, hoping to raise the public’s awareness of environmental protection,” Xu said. “Simba said people should not catch wild animals and then little penguins wouldn’t be homeless.”

He said many people had objected to him taking a young child on such journeys, saying his son would not be able to remember anything at such an age.

“I never pondered if Simba can remember or not,” he said. “I only care if he is having fun or not.”