Tag Archives: Central Texas

Did the first known humans in the Americas live in Brazil or Central Texas?

Recently, news articles have been suggesting that the earliest archeological finding of human inhabitants in all the Americas is at at Toca da Bastiana rockshelter at Serra da Capivara National Park, Piaui, Brazil. At this sandstone overhang shelter, rock paintings of red ochre symbolizing humans, animals, and designs were found.

These “cave-paintings” were found under a 2 mm thick layer of the mineral calcite, suggesting the antiquity of the paintings. Calcite is formed when water deposits calcium-rich minerals on a rock surface over time, which builds up gradually with successive wettings and dryings of the rock surface. Very similar to how stalactites and stalagmites form in caves. When the calcite crystals first form out of aqueous solution, their radioactive decay first begins, and so they keep the radio-carbon “signature” of the time of their formation.

Watanabe et al. (2003) decided to radio-carbon date the calcite layer, since they supposed all the calcium had formed anew from being dissolved in water. They found the calcite to be 35,000 to 43,000 years old, and inferred the rock paintings were at least this old.

This would predate the second oldest known site by over 20,000 years!

Besides this Brazil study, the oldest known Americans lived some 13,000-15,000 years ago, 40 miles northwest of Austin in Central Texas at the Buttermilk Creek complex (Waters et al. 2011). This site is an extensive dig with tons of artifact with lots of support for the dating. A site in Washington and others nearby correspond to this same time frame (Waters et al. 2011b). These sites predate the Clovis culture by a few thousand years. There is an extensive literature and archeological record from the Clovis culture (13-12 kya) forward.

However, Rowe and Steelman (2003) at Texas A&M performed “direct” radio-carbon dating on the paint itself used at the Serra da Capivara rock painting site and found the various images to date from different times 1200- 3600 years ago. They also dated the calcite layer dated by Watanabe et al. (2003), and found it to date only 2490 +/- 30 years before present.

Rowe and Steelman (2003) suggest Watanabe et al. (2003) did not account for the incorporation of calcite dust from the surrounding riverbed / bedrocks into the nascent aqueous calcite that formed the calcite layer in front of the paintings. The incorporation of this calcite dust, which would date millions of years old by itself since it was precipitated out of aqueous solution at the same time as the surrounding bedrock, severely skewed the dating of the layer of calcite over the paintings (Rowe and Steelman 2003). Watanabe et al. (2003) apparently assumed all the calcite they were dating was all formed at the same time from aqueous mineralization, ignoring the possibility of dust being settling on the wet rock face and becoming part of the calcite layer. Rowe and Steelman (2003) conclude “once again, and most dramatically, these studies point to the necessity of independent studies dating rock art.”

Unfortunately many if not all of the news stories out there make no mention of this rebuttal study, which was published just 6 months after the original one. Even both the official websites of Serra da Capivara National Park and UNESCO World Heritage present the 36,000 + year old date as uncontested fact, making no mention of any disputes in the dating. The same websites complain of a dearth of visitors who should be attracted by the extreme antiquity of the rock paintings.

Lets keep things simple and not confuse people out of greed for ticket sales to a park. Humans may well have inhabited Brazil at this time and before all other places in the Americas. But before I believe this, I will wait for evidence that is even remotely comparable to the evidence brought forth by Waters et al. (2011, 2011b) that the oldest known Americans were here no earlier than 15,000 years ago.

Conflict of interest statement: the author was raised in Austin, very near the oldest known pre-Clovis site. Central Texas has the best flint in the world, known to flintknappers as “Georgetown flint,” after the quarry it is commercially dug from in Georgetown. This flint is harder than obsidian, but flakes and works easier than any other type of flint or chert. This area is also anomalously diverse in flora and fauna compared to surrounding ecosystems of Texas and the USA, being at the confluence of five or more distinct ecoregions of Texas. The area is profusely bubbling with pristine springs, resulting from Central Texas’ Balcones Escarpment Uplift and Edwards Aquifer beneath the Cretaceous limestone bedrock. Jacob’s Well was known to be constantly bursting 100 feet high in the air with a fountain of pure springwater during settlement times (though nowadays there is often negative pressure).

I think the first Americans migrated south after reaching the continent, either from the Bering sea, or as the new book Across Atlantic Ice by Stanford and Bradley claims, by following ice sheets from Europe to North America. When they found Central Texas, they dug in, (it being paradise on earth back then) developed maximum carrying capacity sized populations and left extensive archeological records, with their descendents continually occupying the area until extirpation by colonists.

The rock paintings from the Brazil site are pretty cool. I wonder what they mean… who made them, who was meant to see them, and why? Were they just fun doodles by ancient graffiti artists? Part of some mysterious rituals? Recorded history? Instructional drawings? Maybe it’s more fun not knowing, and just guessing from the photos:

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Rowe, M. W. and Steelman, K. L. 2003. Comment on “some evidence of a date of first humans to arrive in Brazil.” Journal of Archaeological Science 30: 1349-1351.

Watanabe, S., W. E. F. Ayta, and H. Hamaguchi. 2003. Some evidence of a date of first humans to arrive in Brazil. Journal of Archaeological Science 20: 351-354.

Waters, M.R., Forman, Jennings, Nordt, Driese, Feinberg, Keene, Hallifan, Lindquist, Pierson, Hallmark, Collins, Wiederhold. 2011. The Buttermilk Creek complex and the origins of Clovis at the Debra L. Friedkin site, Texas. Science 331(6064): 1599-1603.

Waters, M.R., Stafford, McDonald, Gustafson, Rasmusse, Cappellini, Olsen, Szlarczyk, Jensen, Gilbert, Willerslev. 2011b. Pre-Clovis Mastodon hunting 13,800 years ago at the Manis site, Washington. Science 334(6054): 351-353.

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Central Texas Natural History

Central Texas Natural History

The Edward’s Plateau encompasses the hill country ecoregion of Central Texas. The Balcones escarpment, forming a semicircle from southwest to northeast surrounding central Texas, forms the Edward’s plateau to the west, which ends to the west and north with more uplifted terrain. The limestone bedrock of this plateau was formed in the Cretaceous by shallow sea deposits. The plateau uplifted in the Miocene while the Gulf Coast region to the east subsided. Subsequent erosion formed the karst topography characteristic of the area today, with abundant hills, creeks, springs, and caves. The Edward’s aquifer roughly follows the western border of the Balcones escarpment and several other aquifers are found in the plateau.

aquifers of the Edwards plateau and Balcones escarpment

aquifers of the Edwards plateau and Balcones escarpment

google map of the hill country

google map of the hill country. “A” indicates Austin

The climate is mediterranean, with hot dry summers having mean temperatures around 85 degrees Fahrenheit, cool dry winters having mean temperatures around 50 degrees, and rainy seasons in both the fall and spring, in which rainfall is often intense. Over 30 inches of rain in a day is possible. I’ve read it’s the most rain per unit time for any area in the world! Mean annual rainfall is about 30 inches but often varies interannually as much as ten inches.

Savannas are the natural ecosystems representative of the hill country; a patchwork of forests and grass/scrublands, with the latter dominated by little-bluestem grass, prickly-pear cacti, yucca, mesquite, and other scrub which intergrade with forest dominated by Ashe’s juniper (Juniperus ashei) and oaks. Grass/shrublands of this region were historically maintained by fire, bison herd grazing, anthropogenic burning (including by American Indians for as long as since 15,000 years ago), and recently, cattle grazing. Grasslands form early seral stages that over succession would develop more scrub then a climax forest type dependent on local topography if left undisturbed in 50-100 years, when trees form closed canopies.

The grass/scrubland currently occurs in areas where burning or clearing creates disturbed sites preferred by the pioneer plants. The composition of these plant communities varies with habitat water and nutrient availability, in turn largely defined by the local topography. In general, disturbed hilltops are drier than the low-lying terrain. The steep hillsides have intermediate, but more variable microclimate, depending upon local drainage patterns. In general, cacti and yucca thrive in the drier microclimate, thorny shrubs thrive in the wetter microclimate, and though grass is ubiquitous throughout, grass species composition varies with water availability. In areas of extreme local temperature or water stress, such as steep hillsides or clifftops, this will be the climax seral stage.

Juniper-oak woodlands are the typical climax seral stage, with the species composition of the community of these climax stage species varying by local topography. In general, old-growth hilltops are both drier and hotter than old-growth low-lying terrain. All forests are most dominated by Ashe’s juniper (Juniperus ashei). Hilltop forests are co-dominated by escarpment live oak (Quercus virginiana var. fusiformis) and bastard oak (Quercus sinuata). Hillside forests are co-dominated by escarpment live oak and Texas oak (Quercus texana). Lower slope/creek forests are co-dominated by escarpment live oak, cedar elm (Ulmus crassifolia), and Texas oak (Quercus texana). Forest directly beside creeks are dominated by black willow, black walnut, eastern cottonwood, and American sycamore.

Rendering I made of a typical elevational profile from Wild Basin Wilderness Preserve, Austin TX showing tree diversity and biomass increasing from the hill to bottomlands along with the nutrient and water availability

Rendering I made of a typical elevational profile from Wild Basin Wilderness Preserve, Austin TX showing tree diversity and biomass increasing from the hill to bottomlands along with the nutrient and water availability. Names denote select geological formations.

Drawing I made of a typical elevational profile from Wild Basin Wilderness Preserve, Austin TX showing the general ranges of abundant tree and shrub species

Drawing I made of a typical elevational profile from Wild Basin Wilderness Preserve, Austin TX showing the general ranges of abundant tree and shrub species

Plant communities are particularly species rich, with unique combinations of dominant plant species and forms from many ecosystem types since the central Texas ecoregion is at the confluence of five major distinct surrounding ecoregions. For example, pecans and live oaks are dominant in the gulf coast to the east, post oak and junipers are dominant in the post oak savanna to the northeast, grasses are dominant in the prairies to the northwest, yuccas and cacti are dominant in the Chihuahuan desert to the west, and mesquite and other thorny scrub are dominant to the south. As all of these plants can be dominant locally, the flora of central Texas reflects the diversity of the surrounding ecoregions. Similarly, here the fauna is particularly diverse. The abundant caves and springs provide home to many rare and endemic species of animals, from cave spiders to springs salamanders. Bats are common and abundant because of the abundance of caves in which to roost. The historical extirpation or persecution of large predators such as bears, wolves, and pumas, has contributed to ecosystem modification by outbreaks of white-tailed deer overbrowsing.

Fire suppression, bison and American Indian extirpation, and massive decimation of habitats in the region by development and ranching have reduced original savanna to about 2% of the pre-settlement area. Today, protected areas are somewhat distorted representations of the pre-settlement ecosystem since even they do not have fires or bison. The frequency and intensity of droughts have been rising with exponentially increasing human development in the area.

Central Texas is home to the earliest known archeological record of humans in the Americas. Pre-Clovis peoples lived 40 miles northwest of Austin around 15,000 years ago. The area was likely continuously occupied by humans, the last of whom before European settler extirpation, were the Apache and Comanche. These American Indians used burning to improve hunting, thus along with natural fires and bison, encouraged grassland and the savanna matrix rather than forest thickets, common in protected areas today.

References:

A native Texan naturalist (pers. observ.).

Looking north from a hill on Wild Basin Wilderness Preserve

Looking north from a hill on Wild Basin Wilderness Preserve

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