By David Smith at the Cradle of Humankind, South Africa From The Guardian UK

The skeletons found in a South African cave were retrieved by six scientists with a hard-to-find combination of skills

The advertisement on social media called for “tiny and small specialised cavers and spelunkers with excellent archaeological, palaeontological and excavation skills”. And there was a catch: they would work for no pay.

“Why wouldn’t you apply, with an advert like that?” recalled successful applicant Elen Feuerriegel, speaking at the Cradle of Humankind world heritage site in South Africa after scientists claimed the discovery of a new human ancestor. “How could you not? It was the thrill of discovery.”

There were 57 applicants for the excavation: the six chosen were all women. “I suspect that physiology probably played a part,” Feuerriegel said. “I know for a fact that there were male applicants but we were all within a range of size that was appropriate for getting into this cave, and we also had the caving experience.”

The all-female team – Hannah Morris, Marina Elliott, Becca Peixotto, Alia Gurtov, Lindsay Eaves and Feuerriegel – were drawn from Australia, Canada and the US.

Feuerriegel – 5ft 3ins (1.60m), 52kg (8st 4lb) and “pretty skinny” – said: “It was really unusual, in terms of teamwork, how well we got on, because you sort of expect there are going to be small clashes of personality at least, but we got on really great.

“I think a lot of it had to do with a shared goal and the fact that we were sort of in the public eye. As National Geographic was funding the expedition, there was quite a bit of media attention and I think that helped foster camaraderie among us – the shared distaste of being in the limelight all the time.”

The 21-day excavation of the Rising Star cave meant crawling for 20 minutes through a narrow underground tunnel, lit only by head torches, to find a chamber containing what expedition leader Lee Berger, who is too big to squeeze in for a look, described as “the largest assemblage of fossil human relatives ever discovered in the history of the continent of Africa”.

Feuerriegel, who is studying for a PhD in human evolutionary biomechanics at the Australian National University in Canberra, reflected: “You could feel the press of rock on either side but, aside from that, it was actually all right getting in with a little bit of wiggling. It’s a bit crowded, there’s not much room, so we did have to coordinate these yoga poses, the three of us who were down there at any given time to work around each other.

“We often had to trade up positions because someone’s legs would get tired and go numb and they’d have to go and try move delicately over to the next little rocky outcrop in order to get across the remains without crushing anything. There would be a couple standing on the one rock on tiptoes and we’d all have to spider-walk out of there.”

The women were supposed to work in shifts of three hours but often spent twice as long, and “some days you couldn’t pry us out, really, with a crowbar. It was absolutely one of the most exciting experiences of my life. I don’t really have words to describe how thrilling it is to have been involved in it. It feels like the culmination of so much collective effort.”

IMAGE: Lindsay Eaves, one of the six scientists on the caving team that retrieved the Homo naledi specimens, with expedition leader Lee Berger. Photograph: University Of The Witwatersrand/Barcroft

For more on this story go to: http://www.theguardian.com/science/2015/sep/10/homo-naledi-small-spelunkers-required-how-an-advert-led-to-the-discovery-of-homo-naledi