First, the new ages for the Spanish handaxes have several implications, some of which are aptly discussed by John Hawks. The first is that how refined some handaxes are is not necessarily a good indicator of their overall age. That is, biface morphology doesn't simply gradually go from coarse to fine over time, and biface morphology is influenced by many factors and essentially reflect use considerations at the end of an individual handaxe's use-life (McPherron 2000). This was a well-established fact before this new study, but these dates underscore that lack of correlation especially well. A second implication is that the Acheulean (yup, that's how you spell it!) is therefore likely to be much older than previously assumed. The general consensus has been for some years that this industry first appeared in Europe around 600kya (cf. Monnier 2006). The age of 900kya for an Acheulean assemblage in Spain thus pushes back that date of first appearance by several hundred thousand years.
What is more, unless you accept that hominins using Acheulean tools came to Spain directly from Africa (across the Strait of Gibraltar?), this age implies that the Acheulean in more eastern parts of Europe must be even older, though hard evidence of this is currently lacking. The earliest Acheulean site outside of Africa is 'Ubediya, in the Jordan Valley, dating to ca. 1.4mya. Assuming a single origin for Acheulean technology, this would mean that the amount of time it took handaxes to diffuse across the European mainland is effectively cut almost in half and now stands at a maximum of about 500,000 years, a long time to be sure, but much less than the previously accepted almost million year interval. This has some important implications in constraining models of early hominin dispersion in Europe and how that relates to the subsequent development of Neanderthals (e.g., Hublin 2009).
And this would make sense, really, given the usefulness of handaxes as a technological innovation. The thing about handaxes is that they are generally described as unchanging over their 1.6my history, although this impression is based on morphology alone and doesn't really reflect the state of thinking among most scholars involved in Lower Paleolithic research. In a nutshell, handaxes were highly polyvalent from a functional perspective and not putting individual occurrences in proper context is what results in this mistaken impression of stasis (Machin 2009, Nowell and Chang 2009). A contextualized approach to handaxe variability is what allows archaeologists to seize on the richness and diversity of Acheulean behavior (Hosfield 2008). It is also what allows us to make sense of outliers like the Lake Makgadikgadi specimens.
By any standard, at 30+cm in length these things are frikkin' huge! Strikingly, the press release only mentions that these very large items were found, without any discussion of how their size is unusual and what this distinctiveness might mean. These specific artifacts are of uncertain age, and their function is also uncertain - at that size, it is unclear exactly what practical function they might have served, as they would have been rather unwieldy to use, unless they were somehow hafted, in which case their heft might be an indication of their ultimate function. Most people tend to assume handaxes were made and used as stand-alone hand-held tools. This lithic-centric view has led to some conjecture that the skill manifest in handaxe manufacture might have served as a form of 'advertisement' to potential mates by especially technically proficient knappers (e.g., Kohn and Mithen 2009). This has been challenged on both theoretical and practical grounds, most eloquently by Nowell and Chang (2008) who detail how such a model cannot, in fact, be argued to be founded on evolutionary theory as commonly defined.
Machin (2009:35-36) argues persuasively that handaxes morphology cannot be understood by reference to single-cause explanations since "variability is caused by the differing motivations and constraints – ecological, physiological, biological, cognitive and social – which act upon the individual agent at any given point in time." The sheer timespan and geographical distribution of handaxes certainly agrees with her - it's unlikely that handaxes served the same function in all contexts in which they are found. In a way, handaxes are perhaps best understood as an especially useful and versatile technological innovation that allowed them to be if not all things to all (pre-)people at least many things to many (pre-)people.
Getting back to the Spanish handaxes described by Scott and Gibert, this raises some interesting questions. The first among these is why, given their recognized usefulness, such implements would be so scarce when they are first documented in the record - at Estrecho del Quípar (the site dating to 900kya), there is only one handaxe in the assemblage, and based on its morphology (Fig. S4: flake scars are present on both sides of the piece, but is not very extensive at all toward the center of either face) some analysts might consider it a core or bifacially flaked cobble instead of a proper handaxe. To be fair, the authors refer to other studies that show that handaxes are not very frequent in most Acheulean assemblages (i.e., Monnier 2006), and they also describe a contemporary Spanish assemblage that lacks handaxes altogether to explain why and absence or low frequency of bifaces is not necessarily a problem to labeling the assemblage as Acheulean. However, this begs the question of what an Acheulean assemblage actually is if not one that contains handaxes, a question that Gilliane Monnier has addressed in great detail, concluding that
It is time for a comprehensive revision of the Lower/Middle Paleolithic periodization based upon a synthesis of multiple aspects of the archaeological record, including climate, subsistence, landscape use, mobility and exchange, symbol use, cognition, and biological evolution, in order to determine whether we should maintain a two-phase system [Lower vs. Middle Paleolithic] and, if so, how it should be defined. (Monnier 2006: 729)
If that's the case, what can we really say about the oldest appearance of the Acheulean without an in-depth consideration of these complementary - and necessary - lines of evidence instead of only focusing on the presence of large bifacial artifacts?
Hosfield, R. Stability or Flexibility? Handaxes and Hominins in the Lower Paleolithic. In Time and Change: Archaeological and Anthropological Perspectives on the Long-Term in Hunter-Gatherer Societies (D. Papagianni, R. Layton and H. Maschner, eds.), pp. 15-36. Oxbow Books, Oxford.
Hublin, J.J. 2009. The Origins of Neandertals. PNAS 106:16022-16027.
Machin, A. 2008. Why Bifaces Just Aren't That Sexy: A Response to Kohn and Mithen (1999). Antiquity 82: 761-769.
Machin, A. 2009. The role of the individual agent in Acheulean biface variability: A multi-factorial model. Journal of Social Archaeology 9: 35-58.
McPherron, S.P. 2000. Handaxes as a Measure of the Mental Capabilities of Early Hominids. Journal of Archaeological Science 27:655-663.
Monnier, G. 2006. The Lower/Middle Paleolithic Periodization in Western Europe: An Evaluation. Current Anthropology 47:709-744.
Nowell, A., and M.L. Chang. 2009. The Case Against Sexual Selection as an Explanation of Handaxe Morphology. PaleoAnthropology 2009: 77-88.
Scott G.R., and S. Gibert. 2009. The oldest hand-axes in Europe. Nature 461:82-85.