New species of Homo discovered in South Africa

Today the discovery of a new species in our primate lineage has been announced. Homo naledi is the new name for the species, marking its assignment as a close ancestral species. This find is based on the discovery of more than 1500 specimens from Rising Star Cave near Johannesburg in South Africa.

Two articles have been published on the finds. The first describing the new species and the second describing the context of its discovery.

Stomatolites

Stromatolites are trace fossils of the biofilms of blue-green algae that grow around an object such as a shell or oyster. As the algal filaments grow outwards, sediment is continually deposited and accreted onto the surface of the algal mat. The stromatolite increases in size and forms distinctive concentric rings if you break the stromatolite in cross section.

This is an earlier stage of stromatolite development that is growing around half of an inch long bivalve.
This is an earlier stage of stromatolite development that is growing around half of an inch long bivalve.

The outer surface of the fossil stromatolites look quite knobbled in their appearance. These round boulders can sometimes be quite large in the fossil record at Lake Turkana, sometimes reaching a meter wide.

Some of these stromatolites can be up to a meter in diameter.
Some of these stromatolites can be up to a meter in diameter.

Stromatolites grow in shallow, hypersaline pools in shore settings, inhospitable to molluscs and other invertebrates that might otherwise graze on the algae. There are no modern examples of stromatolites found today at Lake Turkana, however there are modern marine stromatolites that are in lagoons in Shark Bay in Australia. A 3D model of a stromatolite from 0.7 million year deposits at Lake Turkana can be seen here;

This is a cross section of a stromatolite that has grown up around an oyster shell.
This is a cross section of a stromatolite that has grown up around an oyster shell.

 

Finding fossils the traditional way

 

Finding fossils and other geological features is best done with a trained eye and on foot, where you can bend down and look more closely at your discovery and possibly pick it up and look at it from a different angle. For many year of fieldwork at Lake Turkana, trained fossil hunters have camped in the fossil areas and go out on daily prospection missions, walking over the landscapes looking for fragments that they identify and document on the surface. 

The team walk across the fossil exposures looking for fossil fragments on the surface.
The team walk across the fossil exposures looking for fossil fragments on the surface.
Fossil hunter bending down to inspect a piece on the surface. Photo Credit: Mike Hettwer
Fossil hunter bending down to inspect a piece on the surface. Photo Credit: Mike Hettwer

The team walk over the fossil exposures looking for fossil fragments and geological indicators, similar to the way that you can search for identifiable objects in the images on fOssilfinder. The fossil hunters have the added advantage of being able to pick up a specimen and turn it over to get a better look at it which can be most helpful in its identification. If a specimen is collected then it is essential that its exact position is recorded. Fossils should not be moved out of context.

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These coloured tracks on the Google image, mark the ground covered by the team over one week. These tracks are a useful indication of which areas need to be further covered.

When a discovery is made by a member of the team, a GPS position is taken as well as a digital photograph and some basic notes about the find. It is also given a unique field number, which is written on the fossil and on a small stone beside this so that the number is visible in the photograph for the database. You find many fossil fragments and artifacts on the surface, some of which are taken out of context as they are found in a dry stream bed or have been eroded out of sediments from above that have since washed away. It could therefore be a younger age than that of the deposits that it is sitting on. Ideally we want to discover a fossil that is in its original context and excavate this carefully to recover it.

This is an image of the excavation of a large and complete elephant skull.
This is an image of the excavation of a large and complete elephant skull.

This discovery of an elephant skull was made by spotting the teeth that were visible on the surface but after excavation the enormous skull was exposed. This was eventually jacketed in Plaster of Paris and lifted safely into the back of a car. You can see a video of this here

Once an important discovery is made, it is collected by the team, following strict procedures. Detailed notes are made about the surrounding sediment and rocks. We are interested to know if there are any nearby sandstones, what texture these sandstones are (coarse grained, fine grained, laminated, bioturbated etc.). We also document the presence of root-casts, rhizoliths, calcrete and quartz pebbles. These are good indicators of palaeoenvironment. We are interested in the presence of snails, fragments of fossil turtle, fish or crocodile, and also the type and colour of the substrate (if it is a silt or a clay, sand or a volcanic ash). These are some of the characteristics that we describe during collection of a specimen. We are hoping that you we can replicate this skill by training new eyes in finding fossils and other interesting features in these images.

Is there more to the genus Homo than we think?

Almost 300 years ago, Linnaeus defined our genus Homo (and its species Homo sapiens) with the noncommittal words nosce te ipsum (know thyself). Since then, fossil and molecular biology studies have provided insights into its evolution, yet the boundaries of both the species and the genus remain as fuzzy as ever, new fossils having been rather haphazardly assigned to species of Homo, with minimal attention to details of morphology.

A paper published in today’s issue of science magazine by Jeffrey Schwartz and Ian Tattersall argues that, historically, fossil specimens have been “shoehorned” into Homo species “without regard to their physical appearance”. They overview recent examples of debate to illustrate significant differences in the ways that researchers are willing to group specimens. They also picture several fossil specimen examples of homo to highlight marked differences between them. The paper calls for a revisit of criteria for species recognition. The reason being that historical classification schemes, and subjective assignment of new fossils, may be limiting how we can build testable models of human evolution.

The Science perspectives paper can be found here: “Defining the genus Homo.” Science 28 August 2015: Vol. 349 no. 6251 pp. 931-932 DOI: 10.1126/science.aac6182

1984: The discovery of Nariokotome Boy

This skull and mandible belong to the 1.6 million year old skeleton of Homo erectus found at Nariokotome on the west side of Lake Turkana, sometimes referred to as the “Turkana Boy” or the “Nariokotome Boy”. This discovery was made by Kamoya Kimeu, on a Sunday morning in August 1984. He was walking up a gentle slope on the southern side of the seasonal Nariokotome River when he spotted a matchbox sized skull fragment, which he recognized as belonging to a human ancestor. No one could have imagined that such a complete specimen would be recovered. As the excavation of the hillside progressed more pieces of skull, teeth, and then ribs began to be uncovered. This turned into one of the most exciting excavations of arguably the most important fossil discovered in east Africa.
Due to its completeness, this skeleton provides unprecedented insight into the body shape, brain size and development of Homo erectus. The Turkana Boy was surprisingly tall, 5’3” (1.6 meters) although he was still an adolescent. He had a slender body well adapted to living in hot climates. Homo erectus was the first human ancestor to migrate out of Africa 1.8 million years ago. Several specimens have also been recovered from sites in China, Indonesia, and Dmanisi in the Republic of Georgia.

A 3D scan of this fossil and others can be found at africanfossils.org

Earliest modern human-like hand bone found in Tanzania

Modern humans are characterized by specialized hand morphology that is associated with advanced manipulative skills. Thus, there is important debate in paleoanthropology about the possible cause–effect relationship of this modern human-like (MHL) hand anatomy, its associated grips and the invention and use of stone tools by early hominins. Here we describe and analyse Olduvai Hominin (OH) 86, a manual proximal phalanx from the recently discovered >1.84-million-year-old (Ma) Philip Tobias Korongo (PTK) site at Olduvai Gorge (Tanzania). OH 86 represents the earliest MHL hand bone in the fossil record, of a size and shape that differs not only from all australopiths, but also from the phalangeal bones of the penecontemporaneous and geographically proximate OH 7 partial hand skeleton (part of the Homo habilis holotype). The discovery of OH 86 suggests that a hominin with a more MHL postcranium co-existed with Paranthropus boisei and Homo habilis at Olduvai during Bed I times.

http://www.nature.com/ncomms/2015/150818/ncomms8987/full/ncomms8987.html

Basalt

Basalt is a volcanic igneous rock with a crystaline structure. It forms when lava rapidly cools.

It can be hard to distinguish from sandstone, especially when weathered, as certain types are lighter brown in colour.

However, its crystaline structure and hardness mean that broken pieces retain sharper angular edges than sandstone and it has a more reflective look to it. The crystaline structure can often be seen on broken surfaces. Basalt is often quite black in colour but can be different shades of brown.

examples of basalt rock
examples of basalt rock