North America suffered a major megafaunal mass extinction around the time of human arrival and climate change. Human arrival: the Clovis complex (13,33-12,600 kyr) is clear in the archaeological extinction. More controversial and sparse evidence for pre-Colvis settlement
Looking globally, there is “deadly syncopation” (Paul Martin) between human first contact and megafaunal extinction.
Boulanger and Lyman (2014, Quaternary Science Reviews) argue that megafaunal decline preceded human arrival and were not caused by humans . Others say the same evidence would drive him to completely the opposite conclusion.Gill et al (2009) see similar evidence but leave the door open to causes.
If an overkill happened, what would the records look like. He develops a simple model of human colonisation and animal populations. In one version of the simulation, slow human population growth (0.5% per year), hunting rate 0.75 animals per person per year. This causes extinction in around 1000 years. You would not find much overlap in radiocarbon dates of humans and megafauna. Extinctions can happen quickly but human population growth occurs slowly. Hence it should be much easier to date extinction events than colonisation events .
Hypothesis: it is easier to detect the ecological impact of a small population of humans than it is to detect the humans themselves in the archaeological record.
Prediction1. Declines in megafauna should precede human archaeological sites when site sampling is sparse.
Prediction 2: Decline should happen first in Alaska, then in rest of North America, then in South America
He does a data synthesis to see when these declines first happened (not extinction date).
In Alaska (Guthrie dataset), initial decline occurs around 15 kyr BP. Oldest reliable archaeological site is 14-14.3 kyr, as expected.
In rest of North America, decline begins at 14.2-14.5 kyr. Best pre-Clovis at 14.6 kyr, best Clovis at 13-13.6
In South America, initial decline around 13.6 kyr BP. S America archaeological sites around 13 kr BP. One anomaly is Monte Verde site in Chile, at 15 kyr BP, oldest site in Americas.
Hence the initial declines in megafauna we see probably indicates the first colonisation by humans, prior to the archaeological records.
Lewis Bartlett: what would it take to falsify overkill?
Adrian Lister: human population increase of 0.5% /year is a huge compound increase over 1000 years. Is there any evidence for this.
Michael Borregard: human debris (stones) should be more detectable than animal bones.
Looking globally, there is “deadly syncopation” (Paul Martin) between human first contact and megafaunal extinction.
Boulanger and Lyman (2014, Quaternary Science Reviews) argue that megafaunal decline preceded human arrival and were not caused by humans . Others say the same evidence would drive him to completely the opposite conclusion.Gill et al (2009) see similar evidence but leave the door open to causes.
If an overkill happened, what would the records look like. He develops a simple model of human colonisation and animal populations. In one version of the simulation, slow human population growth (0.5% per year), hunting rate 0.75 animals per person per year. This causes extinction in around 1000 years. You would not find much overlap in radiocarbon dates of humans and megafauna. Extinctions can happen quickly but human population growth occurs slowly. Hence it should be much easier to date extinction events than colonisation events .
Hypothesis: it is easier to detect the ecological impact of a small population of humans than it is to detect the humans themselves in the archaeological record.
Prediction1. Declines in megafauna should precede human archaeological sites when site sampling is sparse.
Prediction 2: Decline should happen first in Alaska, then in rest of North America, then in South America
He does a data synthesis to see when these declines first happened (not extinction date).
In Alaska (Guthrie dataset), initial decline occurs around 15 kyr BP. Oldest reliable archaeological site is 14-14.3 kyr, as expected.
In rest of North America, decline begins at 14.2-14.5 kyr. Best pre-Clovis at 14.6 kyr, best Clovis at 13-13.6
In South America, initial decline around 13.6 kyr BP. S America archaeological sites around 13 kr BP. One anomaly is Monte Verde site in Chile, at 15 kyr BP, oldest site in Americas.
Hence the initial declines in megafauna we see probably indicates the first colonisation by humans, prior to the archaeological records.
Lewis Bartlett: what would it take to falsify overkill?
Adrian Lister: human population increase of 0.5% /year is a huge compound increase over 1000 years. Is there any evidence for this.
Michael Borregard: human debris (stones) should be more detectable than animal bones.