The First Americans?

National Geographic reports that DNA analysis on a tooth found in a cave on an Alaskan island suggests that humans arrived in the New World relatively recently, about 15,000 years ago. Gee, seems like yesterday!

Read about it here.

Actually this is much earlier than Clovis culture, which until recently was considered to represent the "First Americans," appearing about 11,000 ybp (that's "years before present").

You always have to suspect anything that appears in National Geographic -- they always go for the most dramatic interpretation possible [sells magazines] -- but this seems solid, at least for now. There are many competing perspectives.

Actually, behind this is a major reappraisal, going on for some years now, not only of the timing of human settlement of the New World, but also how humans traveled, how they lived, and where they came from. It used to be assumed that the first humans to enter the Americas were big game hunters who pursued their prey across a temporary land bridge. Now it is generally understood that these new settlers in the Americas were coastal peoples in eastern Asia who pursued maritime prey and were capable of crossing broad stretches of water. The first migration into the Americas was thus not a land migration, but a coastal one that proceeded rapidly north to south, with inland settlement occurring much later.

Here we have yet another example of scientific paradigms shifting -- it happens all the time. Just a few years ago the Berengian Land Walk/Clovis theory was the almost unanimous consensus position among prehistorians and all claims for other interpretations were dismissed out of hand. Scholars tied themselves into conceptual knots trying to find ways to discount contrary evidence. Now, however, a new consensus has emerged, and evidence once conventionally dismissed is now considered to be not only legitimate, but important, while other evidence, once cited as confirming the old paradigm, is now subject to critical scrutiny it had earlier escaped. In other words, what we thought we knew before the shift is quite different from what we now think we know after the shift.

As Thomas Kuhn explained in his enormously important Structure of Scientific Revolutions science normally progresses, not through the gradual accumulation on knowledge, but through periodic radical changes in interpretation [paradigm shifts]. A scientific consensus is thus not something written in stone, but a commonly agreed set of interpretations that is stubbornly defended by the scientific establishment, but can be radically changed once that establishment changes its mind and begins to accept rather than dismiss contrary evidence.

All this has some implications for the current policy debate over the environment. A consensus can change, sometimes radically and quickly. The rapid and radical nature of paradigm shifts, such as is currently taking place in the study of prehistory, should serve to caution those who would base public policy on scientific consensus.