We hiked back to the sleds, where the dogs were barking with their usual inexplicable passion. They had just spent two days hauling the 700-pound sleds up to the summit of the pass, without any idea of where they were going or why, and now they were jumping up and down, straining at their harnesses, desperately hoping to. . .pull the sleds some more! As they happily raced off in pursuit of Schurke, I was marveling at their beastly simple-mindedness until it struck me that we were doing the same thing: eagerly hauling gear across the mountains in pursuit of Schurke for no immediately obvious reason. Was this what he meant by team-building -- building us into a team of sled dogs?

Mawson, the young alpha male dog who ran at the front of the lead team and fought off any dog who got near his food or a female in heat, was motivated by the same imperatives that evolutionary biologists ascribe to explorers: food and sex. Exploration, like war, is a high-risk activity traditionally carried out by males, particularly young single males with the least status and access to food or sexual partners. They are primed by their hormones (and by cultural traditions requiring young men to prove their courage) to take risks and endure the hardships of leaving home because their survival has depended on finding new lands and resources so that they can win wives and feed children. The classic explanation for exploration, ''Because it's there,'' could be more accurately phrased, ''Because I can't get it here.''

Today, even though there are no new lands or resources to exploit -- you need a special permit to hunt musk oxen -- the male biological impulses remain. The explornography business taps into these impulses, and men respond as automatically as the sled dogs. When I asked the guys on our trip why they had come, they tended to talk about the need to prove themselves as tough as the old explorers. ''You feel like such a wimp when you read journals from Starvation Camp,'' Lon said. ''We're complaining about light sleeping bags in May, and they were shivering through the winter in bags of wet, rotting reindeer hide.'' He reminisced fondly about the rigors of Vietnam and said that he got the same sort of satisfaction out of his Arctic trips (especially the all-male ones). Once, when Lon and I were by ourselves, slowly trudging along on skis, he threw up his arms and shouted: ''You know why I do this? At this moment I feel alive!'' Part of me thought he looked ridiculous -- he was an even worse skier than I -- and part of me knew exactly how he felt.

There were, however, some obvious problems with the male/sled-dog theory of explornography. It did not account for the four women on our expedition. They didn't talk as much about proving themselves -- they said they had come more to be with the dogs and see wildlife -- but on the whole they were easily as competent as the men. Julia patiently taught the guys in her group how to ski faster. (Now that I needed instruction, she no longer seemed like an evil drill sergeant.)

The sled-dog theory also failed to account for our alpha male. Schurke may have had the Right Stuff, but he didn't like high testosterone levels on the trail. ''I always try hard to include women on the expeditions,'' he said. ''When it's all guys, they form cliques and the he-men make fun of the wimps. They start hooting and hollering like it's fraternity rush week and taking crazy risks -- skiing across thin sea ice, hiking across glaciers without checking for crevasses. When there are women, the group dynamics are completely different. The trips are much happier and healthier. If the old explorers had brought women with them to the Arctic, the body count would have been a lot lower.''

Today's explorers no longer set out to acquire territory, subdue nature or tame savages (or, like Peary, father children by the native women). They go forth in the name of saving the environment, protecting indigenous cultures, building teams and finding personal enlightenment. Peary was a proud imperialist who claimed the North Pole for America; Schurke and Steger talked about global unity and the problems of the poor. Steger later wrote how, thanks to the diarrhea that debilitated him for most of the trip, ''I gained a deeper understanding of the frailty of the human body and I felt greater empathy for people the world over for whom hunger and ill health are daily facts of life.''

When we camped in the saddle of Sverdrup Pass, I conducted my daily inventory of woes -- besides the sprained thumb, I now had blisters on my heels and a black toenail about to fall off -- and found that I was still unable to feel any greater empathy with the third world. Still, I was becoming more sympathetic to the idea of low-testosterone exploration. After dinner, Julia put on a hilarious one-woman show, playing the great Norwegian explorer Fridtjof Nansen and his traveling companion, Hjalmar Johansen, as they made their manly way across the Arctic's ice floes in 1895. After two years together, they still weren't on a first-name basis and used the formal form of ''you.'' Julia played them with puffed-out chests, talking in the Norwegian equivalent of an Apollo astronaut's monotone:

''Mr. Johansen, it seems my chronometer has stopped. Do you have the time?''

''Why, Mr. Nansen, my chronometer has also stopped. Now we have no way to determine our position.''