The rancorous debate over when people first arrived in America has not helped science.
In 1781, American statesman Thomas Jefferson noted that Asia and America are separated “only by a narrow streight” that would have allowed passage between the two continents. There is no record of any scholarly scorn of Jefferson's ideas about the peopling of America. But in recent decades, anyone wading into the topic has needed skin as thick as a woolly mammoth's. The debate over the first Americans has been one of the most acrimonious — and unfruitful — in all of science.
As reported on page 30, one side of that debate held that, around 13,000 years ago, a group of ice-age hunters from Siberia crossed into North America over Jefferson's “narrow streight” — which, at the time, was an exposed strip of land. Armed with stone weapons, called Clovis points, these hunters spread rapidly across the continent and feasted on animals that had never known humans. The opposing camp argued that people reached the Americas long before Clovis technology appeared — at least 1,000 years earlier.
The histories of these arguments are a case study of poor communication and missed opportunities. One researcher, new to the field after years of working on other contentious topics, told Nature that he had never before witnessed the level of aggression that swirled around the issue of who reached America first. “When people stop listening to arguments and stop looking at data and instead just go with their own beliefs,” he said, “that's when it becomes completely crazy.”
He was referring to researchers who support the Clovis-first model, which was the dominant hypothesis from the second half of the twentieth century until only a few years ago. Researchers who went against that model by reporting even older sites of human occupation endured brutal criticism from opponents who did not give them, or their evidence, a fair hearing. Scientists who supported the Clovis-first model countered that reports of pre-Clovis sites were examples of poor scholarship.
Studies from the past few years now offer a convincing case that humans reached the Americas well before the Clovis culture. Credit for this breakthrough should go to open-minded archaeologists, who were willing to investigate pre-Clovis sites seriously, and to geneticists, for bringing fresh ideas and techniques to bear on the topic. The recent finds and the shift in the debate have triggered a renaissance in ancient-American archaeology. Researchers are reopening sites, re-examining specimens and searching for new sites to determine who the early pioneers were, and how and when they arrived.
As these ancient events are explored, some archaeologists should examine their recent behaviour. If what they lacked could be summed up in one word, it might be respect. Researchers must always consider that they might be wrong, and should look carefully at opposing data and conclusions. At the same time, scientists who make bold claims must marshal an extraordinary case, especially if they seek to topple a dominant model built on many previous studies. Such prescriptions sound obvious, but many scientists forget them, particularly in fields with limited data, such as archaeology.
The various factions could take lessons from those early Americans (whoever they were). These ancient adventurers spurned the well-trodden paths of their forebears to explore new territory. But they would not have succeeded without the help of those who came before and gave them their start.