Let us begin by noting that "Europe" is an arbitrarily defined geographical unit occupied for the last few hundred years or so by people who believe that "Europe" is the Center of the Universe. Therefore, this statement: "The earliest hominin occupation of Europe is one of the most debated topics in palaeoanthropology" is more about European Ego than it is about human prehistory.
Nonetheless, there is an interesting find ... of a hominid mandible ... reported in the current issue of Nature that relates to human prehistory in the region of Western Eurasia.
The mandible is associated with a "Mode 1" lithic industry. This means that the stone tools found in the same stratigraphic unit as the mandible are relatively undifferentiated and probably of the type produced by the earliest European hominids. Often, Mod1 one industries in Africa are pre-Acheulean, somtimes called Oldowan, and tend to be close to two million years old or older. Mode 1 industries occur in much of Eurasia over a much broader, and later, period of time.
The mandible is also found in association with the bones of animals that show evidence, according to the report, of modification by humans. The bones were not made into things (tools or ornaments) but rather, show evidence of butchery of the animals with the use of stone tools.
This find comes from the famous localityof Atapuerca, in particular, the site Sima del Elefante, in Spain. Atapuerca has produced some of the most important early human fossil remains in Europea. This particular mandible is from Level TE9.
There is not a direct radiometric date for this unit, however, several different dating techniques have been applied, including paleomagnetism, cosmogenic nuclides, and biostratigraphy. The sum of these methods (discussed in more detail below) indicates a date of about 1.1 to 1.2 million years ago. Assuming the date holds up, this would indeed be the earliest human bone in Europe.
The authors also claim that this find along with other material from other levels suggests a speciation event in this region. Although the authors are somewhat circumspect about this, they seem to be indicating that this is where (and when?) the human-Neanderthal split may have occurred.
The cave deposits in which this was found are extensive, about 18 by 15 meters in horizontal extent, and cohtaining 16 distinct strata.
Here is a photo of the mandible, part of Figure 2 in the paper:
It may seem difficult to associate such as small bit of bone with a particular type of hominid, let alone even identifying it as a human or human ancestor. But this bone (the anterior mandible) is chock full of diagnostic features, and quite a bit can be said about it. Many features pretty clearly link this fossil with "early Homo" and a smaller number of features provisionally link this bone with the particular hominid found previously at this site, known as Homo antecessor.
The animal bones provide clues to the date. The way this works is as follows: Over time, numerous studies of several different species show that a certain series of changes occurred at roughly the same time for each species (a tooth getting longer, for instance). Meanwhile, certain species are found to appear (because of migration or evolution) or disappear (because of climate change or extinction) at specific times. So, if a sedimentary deposit has a number of different animals represented in it, but no other way of dating it, it is possible to estimate a likely range of dates using the presence/absence and various metrics of these animals (usually mammals).
There is a little carnivore that links to a site dated in Italy at 1.4 mya. There is a rodent that shows up on sites dated to around 0.6 - 1.0 million years old. And so on. The fauna suggest a very broad date range, therfore, ranging from about a half million years ago to a million and a half years ago.
Paleomagnetic dating relies on the fact that tiny iron-bearing particles orient themselves to the Earth's magnetic field under certain conditions. The Earth's magnetic field changes orientation a little all the time, and totally reverses now and then. If you have a period of several hundred thousand years, you can then divide that into paleomag periods. The sediments where this mandible were found, as well as sediments above and below, have been studied in detail. This has been linked to studies of the mammal bones for various levels to produce a reasonable dated stratigraphy of these deposits. Paleomagnetic evidence strongly suggests that the upper part of layer TE16 dates to 0.78 million years ago.
Unfortunately, the paleomagnetics in combination with faunal dates are much more vague than one would ideally like, and it is possible that any of the layers above or below this mandible, and the layer in which it is found, could be of a fairly long time range. So, an additional technique was applied.
This technique, using the radioactive decay of a cosmogenic isotope of Aluminum (Aluminum-26). This isotope is formed with the interaction of cosmic rays and dust, slowly settles on the earth in minute quantities, and then proceeds to decay at a known rate. This technique may be affected by contamination of material moving through sediments, improper collecting, etc. but it can work. In the case of this site, two dates were obtained, one a few layers below the mandible, in layer TE7, dating to 1.13 Million years ago, and another in the layer the mandible was found it, dating to 1.22 Million years ago. Both have standard errors sufficient to not worry to much about this apparent reversal in age, but to suggest that all of the lower layers at this site are about 1.1 to 1.2-something million years old.
In my view, the chronology of this site needs further work, and there are probably many opportunities for this to happen. However, the overall age of this site and the specific ages of most of the layers is probably reasonably well understood, and I'm fully prepared to accept that this mandible and associated animal bones, and the tools, are somewhat over a million years old.
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Carbonell, E. Et Al. The first hominin of Europe. Letter to Nature. Nature 452, 465-469 (27 March 2008) | doi:10.1038/nature06815; Received 15 October 2007; Accepted 4 February 2008
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I love this stuff - Thanks for posting it.
Thanks for explaining the three dating methods. Neat stuff.
I accept that the geographic designation of "Europe" is arbitrary. So, if paleontologists got to make the arbitrary designations, what would they come up with? (One of the points swimming around my brain on this is Carbonell et al.'s association of this fossil with one from the Caucasus and the presumptive migration of early man around the Mediterranean via the mideast. However, I fail to see the Straits of Gibraltar as too big a hurdle for migration from Africa directly into Spain.)
If you'd care to speculate, I'd be delighted to listen.
Going across the Strait of Gibraltar would require a boat, so the question there is who had boats.
To the larger question: I think latitude would be a big factor, and major biogeographical barriers as you suggest. Medium to large scale climate zones are the real answer. But of course these zones change over time.
One thing for sure: Lebanon, Jordon and Israel are in Africa.
I agree you. I'm European but still thought that the "one of the most debated topics in palaeoanthropology" line was a bit much.
"'Europe' is an arbitrarily defined geographical unit occupied for the last few hundred years or so by people who believe that "Europe" is the Center of the Universe."
I hate this too. When will people realize that Britain is much more the center of the Universe than Europe ever was?!?
"Going across the Strait of Gibraltar would require a boat, so the question there is who had boats."
It can actually be swum - it was done recently for charity, and I believe you can see one shore from the other. It's a bit of an endurance feat, but it's possible.
Also, the Mediterranean has a very high rate of evaporation - isn't there some speculation that levels could have radically altered at various times in prehistory? This could have left our ancestors with an even shorter swim...
The med has been virtually empty because of evaporation but that was millions of years before humans, and the crossing points would have been in the Eastern Med.
Regarding the centrality of England ... you inspired me to put up a new post on exactly that topic (well, actually, an old post from my earlier blog).
The timing of the earliest occupation of Europe is a hot topic for a reason beyond European ego: it concerns the question of how many human migrations occurred, when/where they started and which particular branch of Homo undertook them.
This brings in other fraught yet interesting questions -- the biological/cultural/technological status of these hominids, the possibility of branches mingling, etc. Since we don't have molecular information (mitochondrial or Y-chromosomal), we have to rely on the methods that you outline in your synopsis.
You claim:
Lebenon, Jordon and Israel are in Africa.
It's Lebanon and Jordan. And you're wrong.
Eleanor, you've got one chance to explain yourself and it better be good. My readers are very much annoyed by trolls.
(Except the ones that are trolls, of course).
Before you answer, look at a map. On by the way, I'm going to throw the Arabian Peninsula in. That's Africa too. It is hard to draw a certain line in the upper reaches of the twin rivers and the zagros.
Whilst, it may not be one of the hot topics in palaeoanthropology, it's still a subject that has raised a fair amount of debate and can tell us a fair bit about hominid ecology and behaviour. In particular, there is Wil Roebroeks work with the short chronology stuff ("The earliest occupation of Europe: a short chronology" and "The earliest colonization of Europe: The short chronology revisited") and the early British material ("The earliest record of human activity in northern Europe").
This is a decent summary, from a plenary lecture Wil gave a couple of years ago:
Roebroeks, W. (2006) The human colonisation of Europe: where are we? Journal of Quaternary Science, 21,425-435.
This paper focuses on the earlier parts of the human colonisation of Europe and its wider setting and addresses the two basic tasks of archaeologists working in this field: (1) to identify the spatio-temporal patterns of human presence and absence, i.e. getting the pattern 'right'; (2) to explain these patterns. Archaeologists have invested mostly in the first task, while the second one takes us to the field of biogeography. Study of biogeographical limits of hominins necessitates integration of many aspects of a species, e.g. diet, life history and social organisation, and the way environmental factors shape these. Palaeoanthropologists need to combine these with establishing data on the chronology of hominin presence, on palaeoenvironment and climatic oscillations, on emergence and disappearance of land bridges, and so on. They further have to acknowledge the fact that only very small parts of the former ranges of the species have been sampled 'adequately'. The paper explores some of the key issues at stake in dealing with the human colonisation of Europe.
(Except the ones that are trolls, of course). I resemble that remark!
CMF: I know you know enough about the issue at hand (where does Africa end, historically, archaeologically, biogeographically, etc.) ... so I fully expect you to handle Elenah when she comes back.
I like your inclusion of the terms 'historically and biogeographically'...that will throw her off for sure;-)
But...dare I mention those 'other, less likely to be implicated in international terrorist conspiracy' Jews of Northern Africa?
http://www.jewishvirtuallibrary.org/jsource/Judaism/ejtoc.html
That will really flip her lid...er..yamulka...
Thank you for explaining the dating methods. I hadn't heard of them using Aluminium isotopes for that sort of thing before, although I had come across others. I presume they all work in a similar fashion, but on different atomic 'clocks'?
And Martin is correct, the Straits of Gibraltar were swum recently for charity. Sports Relief, if I'm remembering correctly.
Parts of North America are African as well as European. Tectonics is a slut that way, topographical DNA is found all over the place in the most unusual nooks and crannies. The point being the Red sea spreading zone and the Dead Sea transform fault are the geological divides. Processes determine classification not provenance. Just saying.