Filming for Origins gave me the opportunity to do something I've never done before: to observe our closest cousins, chimpanzees, in the wild.

Earlier this year, on 5 March, I met up with a crew I knew very well - we'd filmed before on Incredible Human Journey - in Heathrow's Terminal Five.

We flew to Entebbe in Uganda, then drove some six hours to Kibale - the famous wild chimpanzee research station.

We arrived at the research station at dusk.

We were given a very serious health and safety induction which included: how to behave if a chimpanzee charged at you (stand up tall and wave your arms); how to behave if a forest elephant headed straight for you (stand aside); how to deal with army ants (don't stand on them).

The next day, we set off around 7am, walking into the forest, up a dirt track at first.

We were led by field guide Francis, who had worked at Kibale for 19 years.

On our team, assistant producer Mags Lightbody had been there in those early years, helping to habituate the chimpanzees to human presence.

Dr Alice Roberts holds a chimpanzee at the Uganda Wildlife Education Center. Strict rules in the National Parks mean that no one ever touches a wild chimpanzee in Kibale.

Five field assistants came with us to help carry all our gear into the forest. We turned off the track, down a steep and narrow path.

The forest was dense but the paths were well-used - by animals but also researchers.

Still, there was some pushing through undergrowth and our porters carried machetes to clear awkward or dangerous branches.

The forest was wet and getting steadily warmer as the sun climbed higher above us.

I was getting steadily warmer as well, as we trekked up and down through a series of thickly forested ridges and valleys.

At the bottom of the valleys, we would find ourselves splashing through small streams, or almost getting mired in boggy patches, which had been made even boggier by elephants, their massive, round footprints forming deep puddles.

Climbing a steep slope, Francis paused and whooped loudly, and I heard an answering whoop not too far away.

He was calling to the field assistants who were already out in the forest, with the chimpanzees.

We were very close, and in fact, when he pointed to the top of a tall fig tree just over the crest of the hill, I could see movement amongst the leaves.

Leaving the porters and the bulk of our gear behind, we carried on, as a smaller team, and came across the four field assistants and postgraduate students, all armed with notebooks.

Six or seven chimpanzees were high in the tree, eating a breakfast of figs.

They lay in the crooks of forked branches, reaching out to pick the fruit, and occasionally moving to a new branch, with a rustle and a small shower of falling leaves.

After about half an hour, they started to come down from the tree, and then they were off, knuckle-walking at a fast pace through the forest, and we followed them at a discrete distance.

They didn't stay move as a group. They came down out of the tree singly, although little ones stayed close to their mothers, jumping onto their backs for a lift once on the ground.

They kept in touch with each other with occasional grunts and pant-hoots as they dispersed in the forest, but they also seemed to know where they were headed.

Francis said the fig tree was a favorite place to start the day, but they'd stop off at other trees throughout the day.

They liked eating fruit in the morning, and ate leaves on the ground in the afternoon.

There were about 1800 chimpanzees in the whole forest; the group we were tracking comprised around 50 chimps, but this was also broken up into smaller groups of 15 to 20.

And all the time, groups would be splitting and fusing, with individuals moving between groups - chimpanzee society is very dynamic.

As the chimpanzees moved between trees, they were all around us in the forest, and would often pass by very close, sometimes a metre or two away - which was both terrifying and exciting.

Francis was very aware of where the chimpanzees were around us and would warn us - "There's someone over there," he would say.

The Kibale chimpanzees aren't hunted for bushmeat, and they're never fed by the researchers in the forest, so these chimpanzees viewed humans neither as a threat nor as a source of food.

Getting so close to the chimpanzees whilst they effectively ignored us was a huge privilege.

They were behaving naturally, just getting on with chimpanzee things, whilst we watched them.

Observing chimpanzees in this way is valuable and fascinating in its own right, but it also helps us understand ourselves.

We start to see where the real similarities and differences lie, we can identify the things about humans that are truly unique, when we compare ourselves with our ape cousins - with whom we have a common ancestor, going back some six to seven million years ago.

We had a good day's filming; cameraman Paul Jenkins was delighted that he'd been able to capture so much footage of the chimpanzees.

So, while it was still light, we started to head back to the research station.

We may only have been about a mile away from the compound, as the crow flies, but it took about an hour and a half to get in and out of the forest.

We were all happily tired at the end of the day, and settled down for a well-earned beer and a hot supper.

Going to bed early, I made sure that my mosquito net was safely tucked in under the mattress, and listened to the sounds of the forest again as I dropped off.

We'd be back in the forest again in the morning.

Dr Alice Roberts is the presenter of Origins Of Us.

Origins Of Us starts on BBC Two on Monday, 17 October at 9pm.

For further programme times, please visit the upcoming episodes page.

Comments made by writers on the BBC TV blog are their own opinions and not necessarily those of the BBC.


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