BioQuakes

AP Biology class blog for discussing current research in Biology

Tag: fossil

New Species Related to Humans Uncovered

On September 10th, 2015, the University of Witwatersrand, the National Geographic Society, the Department of Science and the National Research Foundation of South Africa announced the discovery of a new species of human relative, Homo naledi. With more than 1,500 numbered fossil elements, this discovery is the largest fossil hominin find ever made on the continent of Africa. Not only does this finding shed light on the origins and diversity of our genus, but it appears that this new species intentionally deposited the bodies of its dead in a remote cave, an action previously conceived limited to humans.

Homo_naledi_hand

https://commons.wikimedia.org/wiki/File:Homo_naledi_hand.jpg

The species was initially discovered in 2013 in a cave known as Rising Star in the Cradle of Humankind World Heritage Site, some 50 km northwest of Johannesburg, South Africa. The fossils were laid in a chamber about 90 meters from the cave’s entrance, which was accessible only through a narrow chute which required a special team of very skinny individuals to retrieve them. Up and till now the team has recovered parts of at least 15 individuals of the same species. Lee Berger, research professor at Wits University and leader of the expeditions that recovered the fossils said, “With almost every bone in the body represented multiple times, Homo naledi is already practically the best-known fossil member of our lineage.”

Homo naledi has surprisingly human-like features, enough to place it in the genus Homo. It has a tiny brain, about the size of an orange (about 500 cubic centimeters), on top of a very slender body. The research shows that on average H. naledi stood approximately 1.5 meters (about 5 feet) tall and weighed about 45 kilograms (almost 100 pounds). Homo naledi‘s teeth are described as similar to those of the earliest-known members of our genus, such as Homo habilis, as are most features of the skull. The shoulders, however, are more similar to those of apes. The hands also suggest tool-using capabilities. It has extremely curved fingers, more curved than almost any other species of early hominin, which clearly demonstrates possible climbing capabilities.

The most remarkable part of the find is that it has led the researchers to conclude that this primitive-looking hominin may have practiced a form of behavior previously thought to be unique to humanism, intentional body disposal. The space in which the fossils were discovered was so remote that out of more than 1,550 fossil elements recovered, only about a dozen are not hominin, and the few that were not are isolated mouse and bird remains, meaning that the chamber attracted few accidental visitors.

The researchers explored every alternative scenario, including mass death, an unknown carnivore, water transport from another location, or accidental death in a death trap. After examining every other option, they were left to accept intentional body disposal by Homo naledi as the most plausible scenario.

There is still much to be discovered in the Rising Star cave. “This chamber has not given up all of its secrets.” There are potentially hundreds if not thousands of remains of Homo naledi still down there waiting to get uncovered. 

Original Article:  http://www.biologynews.net/archives/2015/09/10/new_species_of_human_relative_discovered_in_sa_cave.html

For more information, check out:  http://news.nationalgeographic.com/2015/09/150910-human-evolution-change/

The Cambrian Explosion: An Evolutionary Arms Race

 

 

About two weeks ago I dropped in on a freshman Biology class on a college visit.  The professor was giving a lecture on something called “The Cambrian Explosion”, something I’d never heard of.  He described the “explosion” as an evolutionary arms race, a period in which the evolutionary process; the diversification of organisms accelerated from 0 to 60 in a “relative blink.”  Needless to say, the lecture piqued my interest, and so I searched the web for some more insight on the curious “explosion.”  I found a great article  from the innovative science blog nautil.us by Brooke Borel called “The Greatest Animal War”. Borel’s article gave me a better idea of what the Cambrian Explosion was all about.

mouth piece

Pictured is a Cambrian Age fossil of Anomalocaris canadensis from the Burgess Shale Formation.  The fossil preserves the mouthpiece of the organism in great detail, and the mouthpiece itself serves as evidence of useful trait acquired during the Cambrian Explosion.

 

 

claw

Above is the grasping claw of the very same Anamolacris canadensis from the Burgess Shale.  The claw is just another evolutionary tool used by the organism to predate and survive.

 

 

Scientists interpret the earliest fossil records (which date from about 580 million years ago) as evidence that early organisms were small, simple, and… soft.  The fossil record shows these early life forms to be defenseless and apparently harmless, lacking the “claws, teeth, limbs, or brains” that are characteristic of competitive, modern organisms (organisms that require these features to survive.)  Mysteriously, around roughly 542 million years ago evolution sped up, and so began what Borel describes as a “period of unprecedented one-upmanship.”  Organisms developed all sorts of mechanisms from eyes; to spikes in order compete with their rapidly diversifying and evolving contemporaries.  According to the nautilus article “most of today’s 30 to 40 animal phyla originated in the Cambrian, and have persisted through time with hundreds of variations on a theme.”  Meaning, that the majority of the ancestors of modern organisms all developed in this 54 million year span.

Now where the University Professor and Borel diverged was on the answer to the questions of “what caused this evolutionary arms race? and “Why did it take an extra billion and a half years for the first eukaryotic organisms to arrive?”  The professor was reluctant to commit to any theory that attempted to answer those questions, having to repeat the phrase “well, we just can’t know for sure,” in response to questions throughout the lecture.  Borel however is more definite in her answer, stating “certainly, the environment around the time of the Cambrian encouraged the explosion as well.  Oxygen had accumulated in the oceans after extreme ice ages… with plentiful oxygen, animals could grow large and absorb the air they needed to breathe through their skin.”  The lack of a definitive answer as to why the Cambrian Explosion occurred hardly undermines its significance as an unprecedented explosion of diversity that has never been repeated in Earth’s history.  The mystery shrouding its roots makes it all the more curious and exciting a topic to read about.

 

 

 

 

 

 

From Fin to Foot

It is widely understood in the scientific community that, at some point, life evolved from aquatic to terrestrial. In that evolution, at some point fish must have evolved into amphibians. The question of this evolutionary jump still remains a mystery, but the discovery of a new fossil has shed new light on the issue, filling in some of the many gaps in this evolutionary story. This new fossil, discovered in Canada was of the Tiktaalik, a proto-amphibian of the Devonian period. Although this species was not necessarily a new find, it was a complete fossil. Prior to the discovery of this specific fossil scientists only had the front half of the Tiktaalik fossil, and as such could only speculate about its back half. The accepted evolutionary story at the time was that front legs developed first as the power behind walking on land, with back legs functioning only as weak supports. However, this new fossil was fully complete and showed a highly developed pair of back legs with a very developed pelvis, quite unlike any found. Although the bones in the fishes back leg were not as complicated as those of modern amphibians, they were far more advanced than the average fish of the time and more advanced than the widely accepted belief of the scientific community had suggested. This Tiktaalik fossil discovered by Dr. Neil Shubin, has fascinated the scientific community, as it is a great example of a creature exhibiting a myriad of evolutionary changes. Although the bone structure development here still favors the fin, there is astounding development in both the fore and hind legs that show that mark this creature as a key link between aquatic and terrestrial life.

This image of the Tiktaalik shows an artists representation of the creature before its powerful hind were discovered

Big Cats of the Past

A snow leopard at the Toronto Zoo The snow leopard is the closest living relative to the Panthera blytheae

In Tibet in 2010  Z. Jack Tseng and Juan Liu travelled to a remote section of the Tibetan Plateau. Whilst there they came across a collection of prehistoric fossils, mostly antelope and other known herbivores, with one notable exception, the skull of a previously undiscovered big cat which they called Panthera blytheae. This skull and the accompanying jawbone fragments belong to what is now, to date, the oldest known big cat. After analysis of its teeth, it has been theorized that this cat would have been quite similar in habitat and hunting style to the modern snow leopard. “In terms of the overall size it would be a little bit smaller than a snow leopard– the size of a clouded leopard and those living cats grow up to around 20kg [44lb],” said Jack Tseng, the discoverer.

Skull of a snow leopard, which is very similar to the skull of the newly found Panthera blytheae

This discovery is quite significant with regards to big cat evolutionary history. Current experts hold that big cats broke from the main felinea subfamily some time around 6.37 million years ago. However, until this find, the oldest big cat fossil was a 3.5 million year old fossil from Tanzania. P. blytheae not only pushes the date back almost two million years, being estimated to have lived between 4.10 and 5.95 million years ago, but also gave weight to the theory that big cats originated first in Asia, not in Africa. Anjali Goswami, a palaeobiologist at University College London said, “This beautiful fossil supports the Asian origin for the group, bringing together molecular, living and fossil data into a unified view of pantherine evolution. It also supports the idea that the Tibetan plateau was, and remains, an important biogeographic region for large mammals and is the center of origin for many important groups. Nailing down the place of origin for pantherines also means that we can better understand the environmental and ecological context in which this group evolved.”

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