Message #261864

[Dekator]

An ancient depository for the dead?

Perhaps most significantly, study of the context of the finds has led the researchers to conclude that H. naledi may have practiced a form of behavior previously thought to be unique to humans. The fossils, consisting of infants, children, adults and elderly individuals, were found in a deep underground room that has “always been isolated from other chambers and never been open directly to the surface,” said Dr Paul Dirks of James Cook University in Queensland, Australia, lead author of the eLife paper on the context of the find. “What’s important for people to understand is that the remains were found practically alone in this remote chamber in the absence of any other major fossil animals.”

So remote was the space that out of more than 1,550 fossil elements recovered, only about a dozen are not hominin, and these few pieces are isolated mouse and bird remains, meaning that the chamber attracted few accidental visitors. The bones show no marks of scavengers or carnivores or any other signs that non-hominin agents or natural processes, such as moving water, carried these individuals into the chamber. Moreover, there was no evidence that the chamber was ever used as an actual living space by humans. “We explored every alternative scenario, including mass death, an unknown carnivore, water transport from another location, or accidental death in a death trap, among others,” said Berger. “In examining every other option, we were left with intentional body disposal by Homo naledi as the most plausible scenario.” This suggests the possibility of a form of ‘ritualized’ behavior previously thought to be unique to humans (“ritualized” meaning repeated behavior.)

The million dollar question: How old?

Now that scientists have discovered this new hominin species, what about the age?

Unlike other fossil deposits in caves, these fossils were found with very few or no fossils of other animals that could be directly associated with the finds, making it impossible to determine a faunal age. The few flowstones in the cave that can be directly linked to the fossils are contaminated with clays, making them very difficult to date. Moreover, the fossils are contained in soft sediments that have been partly re-worked and re-deposited by acts of nature over time, making it extremely difficult to establish their primary stratigraphic position.

“We have tried three approaches that have failed to give dates for the actual fossils, and are currently working on further attempts,” report Berger and the scientific team. “Because of the uniqueness of the fossils and the situation in which they are found, we only want to publish age limits for them when we are absolutely sure that they are right.”

Nevertheless, given the geographic context with proximity to other already dated caves in the area, such as Sterkfontein, Swartkrans, and Malapa, the scientists suspect that the Dinaledi cave system may fall within the 2-to-3-million-year-old time range, possibly placing H. nadeli near or at the root of the genus Homo, considering the morphology. But at this point, it would be an educated guess.

The Expeditions

The story of this discovery really began with two cavers, Rick Hunter and Steven Tucker, who found the entrance to the Dinaledi Chamber and discovered the fossils. They showed pictures of the fossils to Pedro Boshoff, another caver and geologist. Recognizing the fossils as potentially significant, Boshoff alerted Professor Lee Berger, who then spearheaded the assembly of an expeditionary group (called the "Rising Star Expedition") of scientists.

On November 10, 2013 the first of these explorers entered the chamber, initiating the first of two expeditionary efforts, the first lasting about 21 days and the second, in early 2014, lasting about one week. The task was not an easy one. Carefully excavating the fossil elements with tools as delicate as toothpicks and brushes, they gently removed the fossils, piece by piece, and transported them up through the narrow 7.5-inch chute, including a second narrow area called the ‘superman’s crawl’ only 10 inches wide, to the surface. More than 60 cavers and scientists worked together in what Marina Elliott, one of the excavating scientists, described as “some of the most difficult and dangerous conditions ever encountered in the search for human origins”. Elliott was one of six women selected as “underground astronauts” from a global pool of candidates after Berger issued a call on social media for experienced scientist/cavers who could fit through the 18-centimeter cave opening. Social media continued to play a role in the project, as the team shared expedition progress with a large public audience, schoolchildren and scientists. “This was a first in the history of the field,” said Hawks, who worked with Berger to design the media outreach.

The fossils were subsequently analyzed in a unique workshop in May 2014 funded by the South African DST/NRF, Wits University and National Geographic. More than 50 experienced scientists and early-career researchers came together to study and analyze the treasure trove of fossils and to compose scientific papers.

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