Category Archives: genes

Neolithic farming at the northern frontier

The high northern latitudes have been inhabited by humans since the end of the last Ice Age, approximately 12,000 years ago. Conditions that far north, where the Earth’s circumference is about half that at the Equator, are extreme. On the 60th parallel north, for example, the sun is visible for just under 19 hours on the summer solstice, but only for about 6 hours during the winter solstice. Although temperatures may soar above 30°C in exceptional years, the average daily mean is closer to a chilly 6°C (depending on your exact location along the parallel), with record lows in the -30’s–and, of course, you can expect at least a meter of snow in the winter. In other words, this is not an easy place to live even now, with our modern conveniences; it’s hard to imagine what it must have been like for the region’s earliest settlers, who eked out a living by hunting, fishing, and gathering.

A sampling of Neolithic tools. Image courtesy of Wikipedia Commons.

At some point, these intrepid northern colonizers began farming, making use of techniques originally developed in the Fertile Crescent 11,000 years ago. Above the 60th parallel, however, farmers were more vulnerable to climatic stochasticity; archaeologists have uncovered settlements that appear to have been abandoned after the environment became too hostile. In northwestern Europe, exposure to the Gulf Stream allowed Early Neolithic people to initiate farming economies that last to this day. Elsewhere on the continent, however–in Finland, for example–the low average temperature, persistent snow cover, and not-infrequent appearance of summertime snow and ice combined to diminish vegetation periods and make farming a more challenging endeavor.

Until recently, it has been difficult to pinpoint exactly when early Finnish settlers achieved domestication, since there is very little evidence from prehistoric times; the region’s acidic soils took care of the majority of useful artifacts long ago. However, those same conditions are favorable for the preservation of biomolecules harvested from the few remaining pieces of ancient ceramic cooking vessels. Analysis of these fragments–via techniques such as high-temperature gas chromatography, mass spectrometry, and ion monitoring–allows researchers to determine the composition and structure of the molecules, and to look for pre-identified biomarkers. Cumulatively, these characteristics can be used to determine whether the vessels are saturated with aquatic fats (indicating storage of fish and other seafood), terrestrial fats (from species hunted on land), and dairy fats (from domesticated livestock).

Examples of pottery from the Corded Ware period; these pieces date to ca. 2500 BC. Image courtesy of Wikipedia.

Out of a collection of 70 prehistoric fragments unearthed at sites across southern Finland, an interdisciplinary team of researchers was recently able to isolate 19 that were suitable for just such an analysis. The pottery was representative of a range of prehistoric eras, from the Comb Ware period (ca. 6000-4300 years ago) through the Corded Ware (ca. 4800-4100 years ago) and Kiukainen Ware (ca. 4400-3500 years ago) periods, all the way to the Early Iron Age (ca. 2500-1600 years ago).

The earliest molecular samples (dated to approximately 3900-3300 BC) were predominantly marine in origin, indicating a heavy reliance on fishing; the ceramic fragments themselves may have come from vessels used for cooking, storage, or even transport. On the other hand, residues from pottery shards dating to approximately 2500 BC were from terrestrial ruminants. Though they could have come from either wild or domesticated stock, there was evidence of milk fat–indicating that the settlers had begun farming and were now heavily dependent on land animals despite their relative proximity to the coastline. Interestingly, the final Neolithic samples, dating to the Kiukainen Ware period, contained a mixture of terrestrial and aquatic compounds, suggesting that local climate changes may have required a diversification in subsistence techniques. By the Early Iron Age (approximately 1200-500 BC), however, agricultural intensification seems to have allowed population growth and a renewed focus on farming; pottery fragments from this time yielded only dairy fats.

Iron Age pottery (in this case, from Orkney). Image courtesy of Rita Roberts.

Although these patterns may initially seem relevant only to the small portion of researchers specializing in ancient Finnish history, they actually offer some interesting insights to the rest of us, too. For one thing, these archaeological results map nicely onto spatial patterns showing the prevalence of the lactase persistence (LP) genotype–which confers the ability to continue digesting dairy products well into adulthood. While this may be a fairly common characteristic throughout much of the developed West, it is either rare or lacking in parts of the world without a strong tradition of dairy farming. This correlation helps validate the molecular results, and also can be used to draw conclusions about gene flow in Europe. There is a SW-NE gradient of LP allele frequency in Finland, suggesting several separate waves of immigration over the past 6000 years. Further, low LP frequencies in some parts of the eastern Baltic indicate that this region may have acted as a “genetic refuge” for populations who continued to lead a hunter-fisher-forager lifestyle rather than pursuing farming. Pretty amazing that all of this ancient history can be inferred from gene patterns analyzed thousands of years after the fact.

Another interesting implication of the findings is related to what they reveal about how early humans dealt with their difficult and variable habitat. The analyses suggest that animal domestication occurred in southern Finland much earlier than previously thought (ca. 2500 BC), but that use of aquatic resources lasted much longer, post-domestication, than it did in other places settled by Neolithic peoples. In fact, Late Corded Ware Finns appear to have responded to their changing environment by vacillating between hunting/gathering, farming, and some mixture of the two as required. This sort of flexibility is probably one of the major reasons why early settlers were able to maintain populations in such marginal habitat.

Miina Äkkijyrkkä is an artist and dairy farming expert who combined her two passions during a project making cow sculptures from recycled car parts. Images courtesy of the artist, via Inhabit.

The authors of the study write that, even today, “conventional” farming in this part of the world is not for the faint-hearted. A changing climate may prompt humans to push their boundaries ever northwards, but conditions above the 60th parallel will likely always be challenging. If we hope to utilize this “frontier zone” in order to increase food production and make use of the available land, we will probably have to follow our predecessors’ example and demonstrate a willingness to adapt.

Cramp, Lucy J.E. et al. 2014. Neolithic dairy farming at the extreme of agriculture in northern Europe. Proceedings of the Royal Society B 281:20140819.

Feast, famine, and the evolution of the human diet

It’s not easy to keep track of all the different diets out there, but you still may have heard of the “fast diet,” also known as “intermittent fasting” or the “5:2 diet.” Regardless of what you call it, this popular method of slimming down is based on the assumption that it is normal and healthy for our bodies to periodically experience food shortages. Another popular eating regime, the Paleo diet, has been advocated by nutritionists who believe that modern humans should restrict their foods to those available to, and commonly eaten by, our ancient ancestors. This advice is grounded in the idea that our genomes are not very different from those of our predecessors, and are therefore designed not to facilitate the processing of frequent and/or large quantities of “calorically dense foods,” but, instead, of only the freshest and most natural ingredients. Both the intermittent fasting and Paleo diets are thought to promote not only weight loss, but also improvements in general health.

Examples of what Berbesque et al. refer to as “calorically dense foods” (image courtesy of Sott.net)

One of the reasons that eating regimes like these are so appealing is that they sound as though they are grounded in fact–in data collected by doctors, anthropologists, and evolutionary biologists. In reality, however, the logic behind these diets relies on many assumptions. One of these, the focus of a recent project conducted by researchers at the Universities of both Roehampton and Cambridge, is the idea that our hunter-gatherer ancestors frequently experienced food shortages–and even famines. In addition to prompting many a diet, this concept has also influenced theoretical models about the evolution of cognition and various life history traits in humans.

But what if early humans didn’t experience high food insecurity–or, at least, what if the food insecurity they did experience is not that different from what modern agriculturalists are periodically subjected to? Unsurprisingly, this is a question that researchers have previously asked, but their analytical methods may not have allowed them to draw truly informed decisions. For example, past studies have focused predominantly on only a handful of societies that experienced rapid increases in diabetes and obesity rates after swapping traditional diets for those that were more “westernized.” Further, focal groups were characterized according to early ethnographical reports that may not have accurately or fully documented the relationships between various societies and their dietary practices. Finally, and perhaps most importantly, previous work has tended not to account for the fact that contemporary hunter-gatherer groups predominantly live in marginal habitats, and that habitat, in general, is hugely influential in determining both the availability of food and the relationship between locals and the choices they make about sustenance.

Samoan data has been included in previous dietary studies because of increases in type II diabetes and obesity in Samoa since the switch from a traditional diet to one that is more “westernized” and agriculture-based (Image courtesy of Faifeau).

Cumulatively, these flaws prompted the researchers behind the current study to conduct a new set of analyses designed to more rigorously “explore relationships between subsistence and famine risk.” Specifically, they wanted to make three comparisons: first, between hunter-gatherers in warmer (more productive) and colder (more marginal) habitats; second, between hunter-gatherers and agriculturalists, regardless of habitat; and, third, between hunter-gatherers and agriculturalists, with habitat quality controlled for.

Rather than focusing on only a subset of societies at opposite ends of the dietary spectrum, the researchers utilized a global sample including 186 different “cultural provinces”; this included 36 hunter-gatherer societies and incorporated data on eight different variables that each measured a different aspect of famine. They used two metrics to account for habitat quality. The first was effective temperature (ET), which is derived from measurements of both the warmest and coldest temperatures of an area, and also reflects plant growth (with lower ETs generally indicating less abundant vegetative resources). The second habitat variable was net primary productivity (NPP), higher values of which are associated with greater availability of food items.

As you might expect, groups living in warmer climates experienced significantly less famine–and also less persistent famines–than those living in colder areas. Because of this, the researchers decided that their subsequent two analyses would only include data from groups living in habitats with an ET at or above 13 degrees C; this ensured that the analyses were comparing apples with apples, so to speak. Their comparison of agriculturalists and hunter-gatherers revealed that food conditions were more favorable for the latter than for the former. Hunter-gatherers living in warm climates were particularly well off, though both types of society were equally likely to face periods of short-term and seasonal starvation (neither of which was very common). Similar patterns were found when this analysis was re-run with both ET and NPP included in order to control for overall habitat quality. Taken together, these results indicate that–contrary to popular belief–hunter-gatherers are actually less likely than agriculturalists to experience famine.

The Paleo diet aims to emulate the eating practices of our ancient predecessors, both in terms of quantity and type of food items eaten. However, hunter-gatherers likely had access to more foods, and to a wider variety of foods, than we give them credit for–though that is no reason to avoid a diet heavy in vitamin-containing ingredients (image courtesy of Activ8).

In other words, regularly skipping meals and eating extremely low-calorie diets may not faithfully mimic an actual Paleo diet; rather, this way of eating may more accurately reflect conditions in agricultural societies that periodically experience food shortages associated with drought and flooding. Faced with these sorts of environmental instabilities, hunter-gatherers tend to have more freedom to relocate to more productive habitats. This sort of cultural adaptability was also highlighted by the comparison between warm-climate and cold-climate hunter-gatherers, the latter of which engaged in a variety of behaviors (e.g., development of specialized hunting technology, food storage, infanticide, and trade) that maximized survival during times of want.

Given the great importance of culture in mediating the relationships between humans and food, the authors point out that there is no reason for other researchers to assert that our modern food-related health crises are necessarily related to genes. This is the idea behind the “thrifty genotype” theory, which suggests that a subset of our hunter-gatherer ancestors possessed a certain set of genes that conferred better survival and reproduction rates in the face of unpredictable feast-famine cycles.

There may, indeed, be such a genotype, but it is not necessarily an ancient development (it could have evolved since the dawn of the modern agricultural age) and it need not be the only explanation for the prevalence of diabetes and obesity in western societies. Equally–if not more–logical is the idea that some cultures began to favor both “immediate return behavior” (use of resources as soon as they become available, as generally observed in hunter-gatherers living in warmer climates) and a taste for high-calorie foods.

It may be the case that our dietary and lifestyle choices–rather than our genes–should get most of the blame for our current struggles with obesity and weight-related health problems (image courtesy of Dolores Smith).

Centuries ago, when humans were more active and had fewer resources right at their fingertips, this pairing of behaviors would have been adaptive; today, say the authors, it is a liability. They don’t go on to make any recommendations about modern weight loss regimes (after all, they aren’t those types of doctor), but it isn’t hard to read between the lines: Though the intermittent fasting and Paleo diets have undoubtedly worked for some people, they probably aren’t as scientifically grounded as some of their advocates might like you to believe.

Berbesque, J.C., Marlowe, F.W., Shaw, P., and Thompson P.  2014. Hunter-gatherers have less famine than agriculturalists. Biology Letters 10:20130853 (online advance publication).