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Posts Tagged ‘geomorphology

“In a series of forms graduating insensibly from some apelike creature to man as he now exists, it would be impossible to fix on any definite point where the term ‘man’ ought to be used”*…

 

fingerbone

Homo sapiens finger bone, dating back some 86,000 years, found at a site called Al Wusta in Saudi Arabia

 

Darwin turns out to right about the difficulty of dating the emergence of man, not only for the reason he intended (that our emergence from prior species was so gradual as to be indetectable as an “event”) but also because it’s turning out to be difficult to date the earliest examples we can agree are “man” and to figure out when they reached the places they settled…

The Nefud Desert is a desolate area of orange and yellow sand dunes. It covers approximately 25,000 square miles of the Arabian Peninsula. But tens of thousands of years ago, this area was a lush land of lakes, with a climate that may have been kinder to human life.

On a January afternoon in 2016, an international team of archaeologists and paleontologists was studying the surface of one ancient lake bed at a site called Al Wusta in the Nefud’s landscape of sand and gravel. Their eyes were peeled for fossils, bits of stone tools, and any other signs that might remain from the region’s once-verdant past.

Suddenly, Iyad Zalmout, a paleontologist working for the Saudi Geological Survey, spotted what looked like a bone. With small picks and brushes, he and his colleagues removed the find from the ground.

We knew it [was] important,” Zalmout recalled in an email. It was the first direct evidence of any large primate or hominid life in the area. In 2018, lab tests revealed that this specimen was a finger bone from an anatomically modern human who would have lived at least 86,000 years ago.

Prior to this Al Wusta discovery, evidence in the form of stone tools had suggested some human presence in the Nefud between 55,000 and 125,000 years ago. To anthropologists, “human” and “hominin” can mean any of a number of species closely related to our own. The finger bone was the oldest Homo sapiens find in the region.

The bone’s dating contradicts a well-established narrative in the scientific community. Findings, particularly from the area of modern-day Israel, Jordan, and Lebanon, known as the Levant region, have led to the understanding that H. sapiens first made their way out of Africa no earlier than 120,000 years ago, likely migrating north along the Mediterranean coast. These people settled in the Levant and their descendants—or those from a subsequent early human migration out of Africa—traveled into Europe tens of thousands of years later.

Only later, that story goes, did they journey into parts of Asia, such as Saudi Arabia. By some estimates, then, anatomically modern humans would not have been in what is now Al Wusta until about 50,000 years ago.

The fingerbone, then, adds a twist to the tale of how and when our species left the African continent and, with many starts and stops, populated much of the rest of the earth. A new crop of discoveries, particularly from Asia, suggest that modern humans first left Africa some 200,000 years ago, taking multiple different routes…

Politics, geography, and tradition have long focused archaeological attention on the evolution of Homo sapiens in Europe and Africa. Now, new research is challenging old ideas by showing that early human migrations unfolded across Asia far earlier than previously known: “Will Asia Rewrite Human History?

* Charles Darwin, The Descent of Man

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As we return to roots, we might spare a thought for Jean-Léon-François Tricart; he died on this date in 2003.  A physical geographer and climatic geomorphologist known for his extensive regional studies in numerous countries of Africa.

Tricart was a pioneer in many fields of physical geography including the study of a phenomenon central to the migration of early Homo Sapiens, the major dynamic role of climate in landscape evolution.

Screen Shot 2020-05-04 at 4.41.59 PM source

 

“Beneath all the wealth of detail in a geological map lies an elegant, orderly simplicity”*…

 

This year is the 200th anniversary of the publication of William Smith’s extraordinary map, “A Delineation of the Strata of England and Wales with part of Scotland“– the first geological map to identify the layers of rock based on the fossils they contained rather than on their composition.

Smith revolutionized the study of geological time and the order of the succession of life, and established the founding principles for geological surveys worldwide; accordingly, he is considered the “Father of Stratigraphy.”  And as he helped British geology become a science, he is also known as the “Father of English Geology.”

More at “Two centuries of map-making – from William Smith’s survey to satellites,” and at the British Natural History Museum’s page on William Smith.

* Tuzo Wilson (one of the fathers of the theory of plate tectonics)

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As we think about the land in three (nay, four) dimensions, we might spare a thought for William Morris Davis; he died on this date in 1934.  A geographer, geologist, and meteorologist, his most substantial contribution was probably the development of geomorphology, the scientific study of landforms and their evolution.  Specifically, he described a “geographic cycle,” or “cycle of erosion,” explaining the way in which rivers create valleys and elevate land masses.  When Davis retired from Harvard in 1911, the study of landscape evolution was dominated by his theories. Since then, several facets of his theory have been superceded (in part by plate tectonics thinking, as advanced by Tuzo Wilson), though the evolutionary orientation of his theory still informs the field.

Davis was a founder of the Association of American Geographers in 1904, and heavily involved with the National Geographic Society in its early years.  He is considered the “father of American geography”; his home in Cambridge, Massachusetts is a National Landmark.

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Written by LW

February 5, 2015 at 1:01 am

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