scholarly journals Response to Comment on “Evidence of humans in North America during the Last Glacial Maximum”

Science ◽  
2022 ◽  
Vol 375 (6577) ◽  
Author(s):  
Jeffrey S. Pigati ◽  
Kathleen B. Springer ◽  
Matthew R. Bennett ◽  
David Bustos ◽  
Thomas M. Urban ◽  
...  
Keyword(s):  
New Mexico ◽  
North America ◽  
National Park ◽  
Aquatic Plant ◽  
Hard Water ◽  
Ruppia Cirrhosa ◽  
White Sands ◽  
The Last Glacial Maximum ◽  
Lines Of Evidence ◽  
The Last Glacial

Madsen et al . question the reliability of calibrated radiocarbon ages associated with human footprints discovered recently in White Sands National Park, New Mexico, USA. On the basis of the geologic, hydrologic, stratigraphic, and chronologic evidence, we maintain that the ages are robust and conclude that the footprints date to between ~23,000 and 21,000 years ago. Madsen et al . ( 1 ) question the veracity of calibrated radiocarbon ages used to constrain the antiquity of human trackways discovered recently at White Sands National Park (WHSA) Locality 2, New Mexico, USA ( 2 ). The ages were derived from seeds of the aquatic plant Ruppia cirrhosa , which they suggest may suffer from hard-water (or reservoir) effects, making them too old, potentially by thousands of years. We were well aware of this possibility, investigated it, and presented several lines of evidence that argued against such a problem. Here we respond to each of their four primary points.

scholarly journals Comment on “Evidence of humans in North America during the Last Glacial Maximum”

Science ◽  
2022 ◽  
Vol 375 (6577) ◽  
Author(s):  
David B. Madsen ◽  
Loren G. Davis ◽  
David Rhode ◽  
Charles G. Oviatt
Keyword(s):  
New Mexico ◽  
North America ◽  
Last Glacial Maximum ◽  
Critical Assessment ◽  
Glacial Maximum ◽  
Last Glacial ◽  
Independent Verification ◽  
Radiocarbon Chronology ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Bennett et al . (Reports, 24 September 2021, p. 1528) report human footprints from Lake Otero, New Mexico, USA ~22,000 years ago. Critical assessment suggests that their radiocarbon chronology may be inaccurate. Reservoir effects may have caused radiocarbon ages to appear thousands of years too old. Independent verification of the ages of the footprint horizons is imperative and is possible through other means.

Geographic patterns of genetic diversity in North American trees: a continent-wide analysis

2021 ◽  
Author(s):  
Andrew V. Gougherty
Keyword(s):  
Genetic Diversity ◽  
Population Genetics ◽  
North America ◽  
North American ◽  
Tree Species ◽  
Geographic Patterns ◽  
Study Characteristics ◽  
Dispersal Traits ◽  
The Last Glacial Maximum ◽  
The Last Glacial

In the northern hemisphere, many species have been reported to have greater genetic diversity in southern populations than northern populations - ostensibly due to migration northward following the last glacial maximum (LGM). The generality of this pattern, while well-established for some taxa, remains unclear for North American trees. To address this issue, I collected published population genetics data for 73 North American tree species, and tested whether genetic diversity was associated with latitude or longitude and whether geographic trends were associated with dispersal traits, range or study characteristics. I found there were no general geographic patterns in genetic diversity, and the strength of the geographic gradients were not associated with any species or study characteristics. Species in the northern and western regions of North America tended to have more species with genetic diversity that declined with latitude, but most species had no significant trend. This work shows that North American trees have complex, individualistic, patterns of genetic diversity that may negate explanation by any particular dispersal trait or range characteristic.

Evidence of humans in North America during the Last Glacial Maximum

Science ◽  
2021 ◽  
Vol 373 (6562) ◽  
pp. 1528-1531 ◽  
Author(s):  
Matthew R. Bennett ◽  
David Bustos ◽  
Jeffrey S. Pigati ◽  
Kathleen B. Springer ◽  
Thomas M. Urban ◽  
...  
Keyword(s):  
North America ◽  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial

scholarly journals Distorted Pacific–North American teleconnection at the Last Glacial Maximum

2020 ◽  
Vol 16 (1) ◽  
pp. 199-209 ◽  
Author(s):  
Yongyun Hu ◽  
Yan Xia ◽  
Zhengyu Liu ◽  
Yuchen Wang ◽  
Zhengyao Lu ◽  
...  
Keyword(s):  
North America ◽  
Last Glacial Maximum ◽  
North American ◽  
Tropical Pacific ◽  
Glacial Maximum ◽  
Jet Stream ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Tropical Pacific ◽  
The Last Glacial

Abstract. The Pacific–North American (PNA) teleconnection is one of the most important climate modes in the present climate condition, and it enables climate variations in the tropical Pacific to exert a significant influence on North America. Here, we show climate simulations in which the PNA teleconnection was largely distorted or broken at the Last Glacial Maximum (LGM). The distorted PNA is caused by a split in the westerly jet stream, which is ultimately forced by the large, thick Laurentide ice sheet that was present at the LGM. Changes in the jet stream greatly alter the extratropical waveguide, distorting wave propagation from the North Pacific to North America. The distorted PNA suggests that climate variability in the tropical Pacific, notably El Niño–Southern Oscillation (ENSO), would have little direct impact on North American climate at the LGM.

Steering of westerly storms over western North America at the Last Glacial Maximum

2015 ◽  
Vol 8 (3) ◽  
pp. 201-205 ◽  
Author(s):  
Jessica L. Oster ◽  
Daniel E. Ibarra ◽  
Matthew J. Winnick ◽  
Katharine Maher
Keyword(s):  
North America ◽  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
Western North America ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial
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