For more than a hundred thousand years, humans roamed the Earth, foraging for plants and hunting whatever animals they could find. Then, some 12,000 years ago, these hunter-gatherers began to farm.
What prompted the shift?
This transition from hunting and gathering to agriculture seems to have emerged independently in northern China, the Fertile Crescent, Mesoamerica, and various locations in Africa. Some researchers argued that farming offered a more efficient way to get food, but early farming likely wasn’t very productive.
A new paper points out that farm productivity may not have mattered. "Although advantageous, it is not essential that farming productivity be greater than foraging productivity for farming to emerge," write Elizabeth M. Gallagher and her UK-based colleagues in Monday's Proceedings of the National Academy of Sciences.
Instead, a suite of other factors may have kicked off the agricultural revolution, according to their mathematical models.
People were more likely to turn to farming if they were in small, structured groups with farming-friendly property rights, they argue.
“To switch over to a different subsistence strategy is a very risky thing to do,” study co-author Mark Thomas tells The Christian Science Monitor in an interview.
“It’s risky for a number of reasons. One is that it’s a new technology. Two is that it requires a form of property rights, an ability to respect and defend your products,” he says.
“If you were a hunter-gatherer, you were just going out there and taking stuff from wherever from the forest,” explains Dr. Thomas. “It’s not clear that hunter-gatherers would have had any sense that that’s your field, so we will leave that alone, or, this is our forest and we’ll stay here.”
So farming needed to coevolve with a system of property rights, argue both this paper and one from 2013.
The older study, authored by Samuel Bowles and Jung-Kyoo Choi, focused on the emergence of property rights. Drs. Bowles and Choi suggest that farming arose among people who had already settled in an area rich with hunting and gathering resources, where they began to establish private property rights.
When wild plants or animals became less plentiful, they argue, people chose to begin farming instead of moving on.
The new paper confirms Bowles and Choi’s results and elaborates on that scenario.
"Farming is much, much more likely to take off if early farmers were structured into relatively small groups, like family units," says Thomas.
New ideas are much more easily adapted by a small group, he says, while in a large community, it's more difficult to spread ideas, ethics, or rules.
Furthermore, successful farming groups must be more "conservative," Thomas says. "By 'conservatism' what I mean is that if you have a particular strategy you’re more likely to stick to it," instead of switching back to hunting and gathering when farming gets tough, he explains.
Mathematical models vs. intuition
With little archaeological evidence available, the researchers depended on computer models to tackle the age-old question of agriculture's origins.
These models allowed them to manipulate various variables, or parameters, that could contribute to the emergence of farming.
"Fundamentally, we don’t know what the values of those parameters are," says Thomas. Bowles and Choi approached that challenge by manipulating them one at a time.
"We don’t like that approach," Thomas says.
So instead, their team varied all the parameters simultaneously, to see how the model was behaving overall, Thomas explains.
Their model identified which factors – group size, conservatism, property rights, but not field productivity – played key roles in the emergence of farming.
But the question of why comes down to intuition – which the mathematicians hold at arm's length.
"The whole point of modeling is to show things you can’t intuit," says Thomas. "Our intuitions trick us frequently. They shouldn’t always be trusted," he warns.
For example, it’s surprising that productivity may not have mattered to the shift to farming. While we might assume humans would choose to get food in the most efficient way possible, their models suggest otherwise.
Not the obvious choice, but a revolution
Populations might not have all jumped aboard the farm wagon right away. The Monitor's Joseph Dussault reported in April that Northern Europeans might have resisted the shift to agriculture after farming made its way to other parts of Europe. Those researchers surmised that the Northern Europeans might have found that foraging fed them sufficiently, so they saw no reason to change.
Furthermore, farming might not have looked very appealing to people at the beginning. “It would’ve seemed rather unpleasant,” says Thomas, describing the state of human remains from prehistoric farming communities. “You can see in their bones, they look unhealthy, their teeth are bad, they get smaller, unhealthier, poorer nutrition.” This shift might have been from a diet increasingly of grains.
“So it’s really difficult to understand,” says Thomas. “Archaeologists really struggle.” If it wasn’t necessarily more productive initially and was not helping people’s health, why do it?
“It was a true revolution,” he says.
“It was the most profound and important transition in human behavior – human life – in the last million years or possibly even the entire history of the human species,” says Thomas.