Discovery of 1.4 million-year-old fossil human hand bone closes human evolution gap

December 16, 2013

COLUMBIA, Mo. - Humans have a distinctive hand anatomy that allows them to make and use tools. Apes and other nonhuman primates do not have these distinctive anatomical features in their hands, and the point in time at which these features first appeared in human evolution is unknown. Now, a University of Missouri researcher and her international team of colleagues have found a new hand bone from a human ancestor who roamed the earth in East Africa approximately 1.42 million years ago. They suspect the bone belonged to the early human species, Homo erectus. The discovery of this bone is the earliest evidence of a modern human-like hand, indicating that this anatomical feature existed more than half a million years earlier than previously known.

"This bone is the third metacarpal in the hand, which connects to the middle finger. It was discovered at the 'Kaitio' site in West Turkana, Kenya," said Carol Ward, professor of pathology and anatomical sciences at MU. The discovery was made by a West Turkana Paleo Project team, led by Ward's colleague and co-author Fredrick Manthi of the National Museums of Kenya. "What makes this bone so distinct is that the presence of a styloid process, or projection of bone, at the end that connects to the wrist. Until now, this styloid process has been found only in us, Neandertals and other archaic humans."

The styloid process helps the hand bone lock into the wrist bones, allowing for greater amounts of pressure to be applied to the wrist and hand from a grasping thumb and fingers. Ward and her colleagues note that a lack of the styloid process created challenges for apes and earlier humans when they attempted to make and use tools. This lack of a styloid process may have increased the chances of having arthritis earlier, Ward said.

The bone was found near sites where the earliest Acheulian tools have appeared. Acheulian tools are ancient, shaped stone tools that include stone hand axes more than 1.6 million years old. Being able to make such precise tools indicates that these early humans were almost certainly using their hands for many other complex tasks as well, Ward said.

"The styloid process reflects an increased dexterity that allowed early human species to use powerful yet precise grips when manipulating objects. This was something that their predecessors couldn't do as well due to the lack of this styloid process and its associated anatomy," Ward said. "With this discovery, we are closing the gap on the evolutionary history of the human hand. This may not be the first appearance of the modern human hand, but we believe that it is close to the origin, given that we do not see this anatomy in any human fossils older than 1.8 million years. Our specialized, dexterous hands have been with us for most of the evolutionary history of our genus, Homo. They are - and have been for almost 1.5 million years - fundamental to our survival."
-end-
The study was published in the Proceedings of the National Academy of Science this week. Members of Ward's team who helped discover and analyze the bone include: Matthew Tocheri, National Museum of Natural History in the Smithsonian Institution; J. Michael Plavcan, University of Arkansas; Francis Brown, University of Utah; and Fredrick Manthi, National Museums of Kenya.

University of Missouri-Columbia

Related Human Evolution Articles from Brightsurf:

Cell-autonomous immunity shaped human evolution
Every human cell harbors its own defenses against microbial invaders, relying on strategies that date back to some of the earliest events in the history of life, researchers report.

Hunter-gatherer networks accelerated human evolution
Humans began developing a complex culture as early as the Stone Age.

Ancient gut microbiomes shed light on human evolution
The microbiome of our ancestors might have been more important for human evolution than previously thought.

Environment, not evolution, might underlie some human-ape differences
Apes' abilities have been unfairly measured, throwing into doubt the assumed belief that human infants are superior to adult chimpanzees, according to a new study by leaders in the field of ape cognition.

Neandertal genes give clues to human brain evolution
A distinctive feature of modern humans is our round (globular) skulls and brains.

Dryer, less predictable environment may have spurred human evolution
Evidence of a variable but progressively drying climate coincides with a major shift in stone-tool-making abilities and the appearance of modern Homo sapiens.

Evolution of psychiatric disorders and human personality traits
How and why human-unique characteristics such as highly social behavior, languages and complex culture have evolved is a long-standing question.

What gorilla poop tells us about evolution and human health
A study of the microbiomes of wild gorillas and chimpanzees offers insights into the evolution of the human microbiome and might even have implications for human health.

Why expressive brows might have mattered in human evolution
Highly mobile eyebrows that can be used to express a wide range of subtle emotions may have played a crucial role in human survival, new research from the University of York suggests.

Interdisciplinary approach yields new insights into human evolution
The evolution of human biology should be considered part and parcel with the evolution of humanity itself, proposes Nicole Creanza, assistant professor of biological sciences.

Read More: Human Evolution News and Human Evolution Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.