The helicopter descended into our remote camp on Tuesday morning as scheduled. Within two hours the four of us and our gear were standing on a makeshift landing strip of limestone rubble to the south. The helicopter departed for its next destination 200 miles northeast, and the four of us stood in the flat empty landscape waiting for the drone of a Twin Otter plane.

With time on our hands we skipped stones on a shallow pond surrounded by a muddy fringe where the clear tracks of a polar bear made us look around with a bit more care. The Twin Otter arrived and we loaded up and lifted off Devon Island by about 1 p.m. Within an hour we were back at the Polar Shelf research base at Resolute, unaccustomed to the buzz of activity and people. Quite a contrast to the last couple of weeks.

As we departed our field camp we flew over some of the same areas that we had examined in detail during our explorations. Though the view from above was a useful geological perspective, our search for fossils requires that we “get our nose to the rock,” a task that requires a lot of hard work. The sore arms and legs from many miles of rugged walking and splitting rock seems an appropriate sensation, as one of the goals of our research is to understand more about the evolutionary origins of these appendages from evidence in the very rocks we were exploring.

I’m so sore today. Took a long hike, 10-12 miles, over some rock formations that tend to break up into boulders. Up and down, boulder to boulder. Hard work. But we got to see some rock formations we haven’t seen before and we continue to make discoveries.

Our last day is tomorrow. We’ve had a relatively short season compared to our six other Arctic expeditions, but we really worked this area hard. We covered 35 square miles on foot and surveyed additional areas when flying in by helicopter. Logged 13 fossil sites, meaning there are enough fossils at these sites to log them, to take geographical information, and to collect fossils to bring back.

We’re finding an awful lot of the same creatures we found before: armored fish and lobe-finned fish, but nothing in the limbed realm. What’s interesting is these same rock formations further to the east produced large numbers of a fish called Psammosteus, but there are none here. This shows ecological differentiation. Maybe we’re too far out into the delta system, too far away from the prime area where that type of fish seemed to have lived.

The common thing we’ve seen across all the various environments and time periods is Bothriolepis, a small (about 12 inches long) heavily armored placoderm fish. It’s presumed that Bothriolepis spent most of its life in freshwater, but was probably able to enter salt water as well. Some hypothesize that they lived most of their lives in saltwater and returned to freshwater to breed, similar to salmon. It had a long pair of spine-like pectoral fins which may have been used to lift its body clear off the bottom, but its heavy armor (that protected against predators) would have made it sink quickly.

So we need to look at that common animal and see if there are patterns, where they are found, the great diversity of them. What does that tell us? This is all part of what we’ve been doing this trip: putting the final touches on the bigger project. Over our seven trips to the Arctic, we’ve systematically surveyed many rock formations through the Late Devonian Period and across a geographic transept.

Everything we find is new because no one has ever reported any of these fish from any of these locations. Some things are expected some are unexpected. The big picture has to wait a little. I’ll be thinking of some preliminary conclusions.

The weather has deteriorated to normal Arctic conditions. Winds are gusty at 15 to 20 mph and it’s cold. I’m wearing a wool hat and gloves. Sleet is hitting my tent. We got pretty spoiled with the milder weather earlier.

The rocks here really augment the rocks we have in Pennsylvania. Between the Pennsylvania research and the research here we are getting a good picture of the different animals that lived in the Late Devonian period. The types of environments they lived in.

This place is full of a lot of small discoveries and only a few big discoveries. We’ve had a lot of big discoveries both in Pennsylvania and the Arctic and have lots of continuing work to do.

This year so far is characterized by discoveries that are helping us answer questions about the variety of life, the biodiversity of life, the environments where life was diversifying and flourishing. The most interesting aspect of what we’re looking at is the transformation from finned to limbed animals. But we want to place that transition into the environmental context. That’s why we are collecting so much data.

We working one rock formation called the Nordstrand Point formation. That is from a slice of time which is more recent than where we found Tiktaalik. It’s not as recent as the work in Pennsylvania. It’s a slice of time we would really like to know what was going on, the stream systems, deltas, swamp habitats. We’re finding plant material, nature of the rocks and fossils, a variety of fish. Some are just like things we’ve seen elsewhere.

The most common fossils we’re finding are placoderms, plural for a group of armored fishes. Every day we see them at every site. We’re also finding other groups of animals, but we won’t know what we have until we get back to Philadelphia and do the fossil prep work in the lab. The library work to identify what we have. The payoff comes months after the actual field work itself.

The team is doing great. It's just the four of us -- Neil Shubin from the University of Chicago, Marcus Davis, a professor in Georgia, and Mark Webster, a professor at the University of Chicago who studies trilobites -- and we’re getting along well, which is important.

Every day we make a plan and go out and do what we need to do. We keep a regular schedule. We get up at 6 or 6:30 a.m. We need to check in by radio with the research base at 7:30 a.m. every day. Then we start to work at 8 a.m. We come back to our base camp at 5 or 5:30 p.m., prepare dinner and eat it around 7 or 7:30 p.m., then we’re in bed by 9 or so. There’s not a lot of entertainment up here. We read books. Neil brought a Kindle.

Tonight we’re going to have pasta with red sauce. We make some really good food. We do pay a lot of attention to food and to preparing the food. Usually we have pasta or a chili dish. Big one-pot foods, comfort foods. We eat lots of chocolate, energy bars and coffee. For breakfast we have coffee and granola.

It’s terrific weather here, startlingly warm -- in the 50- to 60-degree range. More importantly, it’s clear and sunny. Hard to sleep because the sun is shining all night long, even though we have blinders to put on.  I’m a little tired. The sun hasn’t gone down since I’ve been here, and it won’t go down the whole time I’m here.

I did some calculations with the GPS, and we’re 700 miles above the Arctic Circle and 900 miles from the North Pole, so we’re about halfway between the circle and the pole. We’re so far north that the sun doesn’t go down for months.

The landscape is rocky, and when I get up high I get great views of the sea. There is pack ice in some places and open water in others. That is appropriate for July. People back home ask about global warming, but we cannot be the judge of that. When we come to the Arctic from year to year, we do not go to the same place. We go to different locations, so we can’t compare the amount of ice and water from year to year.

It’s been a very good couple of days so far in this remarkably remote and rugged terrain. We’ve had exceptionally good weather, in the 40- to-50 degree range, but no rain and no strong wind. And lots of sun. You wake up in the middle of the night, and it’s sunny. At this time of year the sun shines all the time. Maybe it will help me get over the cold I caught before I got here.

Even though it’s only been two days into the trip, I’ve already collected a few very interesting fossils. The plan is to go back to the same site tomorrow or the next day and spend the whole day breaking rock and excavating and seeing what else I might find.

These fossils won’t make front-page news, but they are scientifically very interesting in filling in the story of animals that lived in the Late Devonian Period. That is the window of time we are working with here. Tiktaalik roseae, which I found on an earlier expedition, was one side of that.

We’re not trying to find more Tiktaalik. We’re expanding into the rock formations above and below where Tiktaalik came from and looking for almost anything. But of course the real prize would be something evolutionarily related to Tiktaalik, something showing us another step in that transition of fish to an animal with limbs. But we really can’t come up here expecting to find that.

I’m sitting in my tent in the middle of nowhere. You can’t believe what I’m looking at right now. I’m on Devon Island, the largest uninhabited island on earth. This is an amazing place. The terrain is almost like Mars. It’s just rocks and cliffs.

Devon Island is located in Baffin Bay in Nunavut. The island has northern piece called Grinnell Peninsula. We are on the eastern edge of Grinnell Peninsula, about 5 miles south of Tucker River. We’re camped at a river in a valley, but the river and valley don’t have a name. There is so much land up here and no one has given it names. It’s likely no one has ever been in the valley we are exploring. The Tucker River has been explored a little by geologists. But where I am is untouched by any scientist.

Everything went smoothly earlier this week getting from the research base at Resolute Bay to our remote destination. The people who do logistics for the base were able to organize and orchestrate the process of inserting us into the research site that we had carefully mapped out ahead of time.

For the trip directly north of the base, my colleagues and I squeezed into a small Twin Otter plane along with all our gear. It’s a rickety old plane and a rugged ride, but the plane is efficient up here in this situation. We flew an hour directly north from the research base and landed on a remote strip of Devon Island.

The base crew also had sent up a helicopter, which landed shortly after our plane landed. We then transferred everything to the helicopter and in two trips the helicopter took us to the vicinity of where we wanted to start our field work.

Left Pennsylvania 36 hours ago, now 500 miles above the Arctic Circle. Each step has gone like clockwork, still one step to go, so I hope I haven't jinxed it.

First step was an eight hour drive to Ottawa where we got a few last provisions and ate the last fresh food for a while. This morning we started with a 3-hour flight to Iqualuit, the capital of the Nunavut Territory.

As we moved north at 31,000 feet of altitude and 450 miles an hour, the immense size and emptiness of northern Canada became obvious. By the time we crossed over the entrance to Hudson Bay and began to cross Baffin Island, we were well above tree line. Iqualuit (formerly called Frobisher) has a bustling frontier-town feel and we all commented on the growth since the last time we were there a few years ago. Nunavut seems to be booming as resource extraction is receiving more investment, and perhaps access becomes easier with longer summers without pack ice.

Food is a big part of the quality of life during our field season in Nunavut. The landscape is austere, the temperature is low (35-45 degrees), the days are long (actually, July it is one long day), and camp life is fairly monotonous. Food is sustenance and calories, but it is also entertainment and comfort.

We go to considerable effort to bring quality foodstuffs, most acquired from Trader Joe's, Whole Foods, Sam’s Club, Starbucks, and the Chestnut Hill Cheese Shop. Our buying trips in May usually elicit questions from the stores’ staff as we load our baskets with pounds of chocolate, coffee, granola, and other commodities.

After our shopping forays we spread out our harvest in a research area at the Academy of Natural Sciences and un-package, vacuum seal, consolidate, count, inventory, and pack the food for its northbound journey. We provision our food carefully to avoid excess weight and packaging. Cans, for example, are heavy and create trash – we don’t bring any canned food.

Key elements of our breakfast and lunch are good coffee, granola, fine salami and cheese, hearty crackers, candy bars, and energy bars (usually Clif, but we’re trying some more varieties this year). Cooking dinner is part of our limited entertainment options. We often start with dried beans and dehydrated elements (meat and vegetables) that are brought back to life in a pressure cooker.