The first thing we need to know in order to answer this question is a little background on who Doris Lessing was and what her background and childhood were like. Having been born in Persia (modern-day Iran) in 1919, she and her family relocated to Southern Rhodesia (now Zimbabwe), where she spent her childhood on her father’s farm. Growing up in southern Africa during this time meant growing up in an environment in which racism was everywhere, and as a person with white skin, Doris would have had innumerable advantages and opportunities that were not afforded to those with darker skin.

The first indication of her upbringing having an impact on this story is when Jerry notices that the boys swimming near the rocks are different to him based on the color of their skin. Lessing then depicts how badly Jerry wants the approval of these boys, which is quite ironic, given that at the time in southern Africa, the approval of a black man would have meant less than nothing. The fact that these boys were able to hold their breath long enough—with seeming ease—to swim through the tunnel, when Jerry could not manage this feat, is an interesting reversal of the fact that those with white skin were the ones with privilege in Southern Africa at this time. White people were the ones could do whatever they liked effortlessly, while for those of darker skin, everything—down to their last breath—could be a struggle.

Doris Lessing offers Jerry's experiences as a coming-of-age story in which the boy develops personal skills and gains a sense of pride and achievement. Jerry is inspired to embark on the mission to swim through the tunnel by his interactions with the local boys. While the author does not specify the other boys' race(s), they are dark while Jerry is fair. They are apparently native to the area, while the white child is a tourist or foreigner.

Lessing grew up in a highly segregated colonial society in which children might have sometimes played together but were discouraged from forming friendships. As adults, many Europeans and most official policies promoted white superiority and anti-black discrimination.

Jerry initially wants to hang out with the dark boys, but they are older and make fun of him. He sees their abilities as natural because they are bigger and stronger. Rather than interact with them further and seek their guidance to master the necessary swimming techniques, he isolates himself from them. In contrast to what he sees as their natural abilities, he uses technology (the goggles), intellect, and hard work, analyzing the task and persevering to develop the necessary skills.

Jerry's successful swim through the tunnel thus symbolizes the white Europeans's conquest of an alien environment through skill. His coming of age coincides with his rejection of social engagement with the dark natives, symbolizing the white colonists segregated policies. Once he has conquered this hostile natural environment, like other colonizers, he loses interest and will, we infer, seek other lands to conquer.

Lessing’s childhood in Rhodesia (now Zimbabwe) was not a happy one. Lessing found herself caught between worlds in a number of ways. For example, though she loved the freedom of the outdoors, her mother's ideas of propriety encouraged her to remain inside and isolated. She was packed off to an all-girls Catholic school, which she left at age 14.

The story builds on these experiences. It is clear that Jerry is caught between two worlds, the world of his mother and the wider world represented by the local boys. Perhaps like the young Lessing, Jerry is fascinated by the mystery of the underwater passage. He intuits that these boys have a skill, a knowledge of the world, that he lacks, specifically because he has been raised apart from them. It is a challenge he cannot resist. When he manages to swim through the passage, he emerges a different person. I do not know if there was a similar “moment of truth” in Lessing’s life, but for Jerry, this moment marks the beginning of his adulthood.

Lessing's story "Through the Tunnel" was published in 1955, one year before she was declared a prohibited alien in her former home of Southern Rhodesia (now called Zimbabwe). While the allusions to apartheid—an often violent policy of segregation and political and economic discrimination--are fairly subtle, the mention of the dark boys who are far from the tourist beach hints at this segregation. This racial separation is probably the cause of the dark boys' surprise that Jerry wants to interact with them, as well as their quick departure.

That they are physically superior to Jerry may be Lessing's way of suggesting the inequity of apartheid, and that Jerry finally swims through the tunnel wearing goggles also suggests that he needs more protection than do the other boys because he is softer, being raised by a mother who dwells on a higher level of society. This contrast between the lives of the native boys and Jerry is evinced in this passage about the other beach away from that of the tourists:

It was a wild-looking place, and there was no one there; but she said, “Of course, Jerry. When you’ve had enough, come to the big beach. Or just go straight back to the villa, if you like.”

Another aspect of the story that may allude to Lessing's own experiences is the placement of a widowed mother for Jerry. For, in the early fifties, many women had to raise their children by themselves since their husbands had been killed in World War II.