Beginnings of agriculture in Europe

In the Winter 2007 issue of Planet Earth, Glynis Jones, Caitlin Buck,Mike Charles, Tom Higham and Sue Colledge talk about their project to date the spread of agriculture into and across Europe using the appearance of cereal grains. They found that agriculture spread rapidly from Greece (where it first entered Europe from the Middle East) along the Mediterranean coast to Iberia, but the spread inland came more slowly, in a “stop and go” fashion.

Previous studies of the spread of agriculture were based on proxies – wood charcoal and pottery – that were easier to date.  Improved technology allows the authors to date much smaller samples, opening up the possibility of actually dating the products of agriculture – charred grains.  While this can create false positives (after all, you can acquire grain through trade even if you aren’t growing it), it seems like a very powerful approach.

H/T Agricultural Biodiversity Weblog

Human impacts on pre-Columbian tropical forests

When European naturalists first visited the New World Tropics they saw vast forests that seemed untouched by humans. While indigenous people often lived in these forests, their populations were small. This led to a perception of tropical forests as primeval, “virgin” forests. In the last few decades, this perception has changed – large areas now covered by mature forests have a history of cultivation. In many cases, “primeval” forests are less than 500 years old.

La Selva biological station in Costa Rica is one of the premier research stations for Neotropical biology. Prior to archaeological study of the site, much of it was assumed to be free of human influence. However, the discovery of pre-Columbian artefacts led to the discovery that the site had been occupied at least 3000 years ago. Charcoal was more abundant in alluvial terraces (flatter areas with deeper, more fertile soil) and less abundant in the less fertile upland soils. A chronology, established by Sol (2000)*, divided the La Selva into four archaeological phases: La Cabaña 1000 – 1550 CE; La Selva 500 – 1000 CE; El Bosque 300 BCE– 500 CE; La Montaña 1500 –300 BCE.

To better understand the history of the site, Lisa Kennedy of Virginia Tech and Sally Horn of the University of Tennessee, Knoxville, undertook a study of sediment cores extracted from the Cantarra swamp*, a 0.5 ha wetland dominated by perennial herbs. They used pollen, charcoal and macrofossils to reconstruct the environmental history of the site. Wetlands are frequently used to reconstruct vegetation histories. As sediments accumulate in bodies of water, plant pollen, fern spores and charcoal fragments are trapped. Pollen coats are extremely tough, and decay takes place very slowly in waterlogged soils. If the vegetation surrounding the site changes, different types of pollen will be deposited into the site. Someone with the patience to sort through these cores can observe thousands of years of history in a few metres of sediment.

The most obvious evidence of human activity is the presence of corn (Zea mays subsp. mays) pollen. Corn is a cultivated species which does very poorly without human intervention. Thus, the presence of corn pollen in the wetland sediments is direct evidence of agriculture. Corn pollen shows up from 880 CE to somewhere between the mid-1600s and mid-1800s. Pollen of other species like Amaranths, Asteraceae (the sunflower family), and other grasses and herbs also peak during and before the “corn zone”, often at the same time that charcoal density peaks. This may also reflect cultivation, although it could represent weedy species establishing after fires. Corn pollen was found in sediments about 1300 years older at another lake about 2 kn distance from this one. The authors suggested that disturbance in this time period at Cantarra swamp may have represented the cultivation of root crops (which don’t leave the kind of pollen signature that corn does.

As a forest ecologist, I find some of the “other evidence of disturbance” to be the most interesting. There are several peaks of Cecropia pollen, and to a lesser extent Trema pollen. These are fast-growing species that are usually associated with large gaps in the forest – specifically the type that human agricultural activities may have suggested. Other peaks of pollen belonging to forest species suggests that periods of forest recovery were interspersed with the cultivated times.

This is very interesting stuff. We are too inclined to interpret forests as “primeval”. In many cases, what our eyes see as ancient is only a few centuries old. It is important to understand that if we want to construct realistic models of forest dynamics.

1. Sol, C., R. F. 2000. Asentamientos prehispánicos en la Reserva Biológica La
   Selva, Sarapiquí, Costa Rica: Sistemas de explotación de recursos naturales
   en un bosque tropical lluvioso. Licenciatura thesis, School of Anthropology and Sociology, University of Costa Rica.
2. Lisa M. Kennedy, Sally P. Horn. A Late Holocene Pollen and Charcoal Record from La Selva Biological Station, Costa Rica. Biotropica (OnlineEarly Articles). doi:10.1111/j.1744-7429.2007.00334.x

Intelligent design and archaeology

One of the arguments repeated over and over by intelligent design advocates is the assertion that archaeology is a search for design. Like intelligent design, they say, archaeologists assume design once they have ruled out other possible causes, so why shouldn’t IDists? I have always found that analogy annoying – after all, it fails to take into account that archaeologists are working with known designers and known mechanisms. But I never really thought the whole point through. Luckily for me, archaeologist Christopher O’Brien has done just that in an excellent blog post (one of many, based on a quick look at his posts). O’Brien writes:

What Egnor and other ID advocates fail to recognize is that archaeology does not assume design…. In my archaeology class I show the students an “arrowhead”… Most students will recognize a projectile point as such, as would most ID advocates, and most will clearly infer a human designer. But then I ask, “How do you know that’s a projectile point?”… Most students will say that they have seen similar items, read about such things in books or articles, or even tried to make one themselves. As we walk through this exercise, students begin to realize that their assumption of human design is correct, but what on the surface seems obvious is in fact built on a large body of previous knowledge…. It took a long time (and a significant amount of written argument) before such design could be attributed to human intelligence.

Not only has O’Brien demolished the analogy, he also manages to draw in one of the fundamental dishonesties of the ID movement. While they continually argue that it is unscientific to speculate on the nature of the designer, archaeology only is able to attribute design as a consequence of a thorough study of the designer.

O’Brien goes on to draw the correct analogy between archaeology and intelligent design: Chariots of the Gods?, Erich von Däniken‘s book that asserts that many archaeological items are too complex to have been made by humans and are thus evidence of extra terrestrials (who were the “Gods” of ancient peoples). While I have a certain soft spot for von Däniken’s woo, since his books were a staple of my childhood (and a net positive element, since they introduced me to ancient cultures I had never heard of, and probably made me one of the few 9-year-olds who had heard of the Epic of Gilgamesh and its relationship to the bible), it really is the perfect comparison.

O’Brien’s closing line is one that deserves to be widely quoted:

Archaeological principles, like those in evolutionary biology, are backed by volumes of data from diverse disciplines. They are not analogous to intelligent design, unless taken out of context. Intelligent design has much more in common with Chariots of the Gods? than it does with Stone Age Spear and Arrow Points of California and the Great Basin.