PERSPECTIVES

ANTHROPOLOGY Trace element and isotope analysis of basalt adzes demonstrates long-distance voyaging Tracking Polynesian Seafarers paths used in East long before European arrival. Ben Finney

bout 4000 years ago, Stone Age from various narratives and committed other These efforts supported the hypothesis that voyagers from Island Southeast Asia scholarly sins. Nonetheless, the unedited tradi- Remote Oceanians were capable of purpose- Abegan to sail east into the Pacific, tions, and increasingly sophisticated linguistic fully making long navigated voyages and set- where they settled the previously uninhabited comparisons, suggested migration paths. tling distant islands. islands of Remote Oceania (Eastern Melanesia, During the past century, ethnologists and Unfortunately, pottery making declined Micronesia, and Polynesia). As Europeans archaeologists sought to trace these paths by after Lapita voyagers reached the mid-Pacific, began exploring the Pacific, they were sur- comparing artifacts from various islands, and was not spread farther east by their Poly- prised to find that mid-ocean islands were but with mixed results. Canoe comparisons nesian descendants. Moreover, although obsid- occupied by seemingly primitive seafarers, became mired in turgid debates over canoe ian occurs in and Easter Island, who had only slim canoes carved with stone typology, outrigger attachments, and migra- tools made from this type of volcanic glass adzes, powered by mat sails, and navigated tion waves. Stylistic comparisons of temples, were apparently not widely spread from these without instruments. Some Europeans could adzes, and fishhooks fared better, but often peripheral islands. not accept that such seemingly ill-equipped foundered over whether features from differ- In the 1980s and 1990s, archaeologists people had settled the islands on their own. ent islands were similar because of a common therefore turned again to stone adzes, particu- They instead imagined such scenarios as origin or convergent . larly those made from fine-grained oceanic storms or currents pushing coastal people far The breakthrough came in the 1960s and basalts of the “hot-spot archipelagos” of East out to sea, the sinking of a great conti-

nent leaving only high peaks and on August 17, 2009 surviving inhabitants above water, and the special creation of on the islands. A few prehistorians still begrudge the Remote Oceanians only minimal seafaring skills, but more than two centuries of research have led to widespread appreciation of their nau- tical capabilities. On page 1907 of www.sciencemag.org this issue, Collerson and Weisler (1) confirm the wide extent of Polynesian voyaging by chemically tracing basalt adzes found on coral atolls to specific Sailing Hokule’a from Hawai’i to Tahiti via the Tuamotus in 1976. volcanic sources. Not until the late 1700s did foreign explorers 1970s, when the discovery of distinctively Polynesia. This time they used major-element

consider seriously how canoe people could have decorated Lapita pottery enabled archaeolo- composition to trace each piece of basalt Downloaded from actively settled the Pacific. Captain Cook and gists to track the rapid entry of the Poly- back to its geological source. This approach Joseph Banks judged Tahitian sailing canoes nesians’ ancestors into Remote Oceania. The allowed intra- and interarchipelago connec- and navigation methods fit for long voyages. By many potsherds proved ideal for stylistic com- tions to be traced over much of Polynesia, but comparing Tahitian words with those gathered parisons, and in some cases, geologists were did not always allow the precise sources of the from islands far to the west, they realized that able to source constituent temper sands to basalts to be identified (7). Tahitian was related to languages of the “East islands near and far. The wide range of Lapita To more precisely source basalt adzes col- Indias.” Upon hearing from the Tahitian savant voyaging was demonstrated even more dra- lected over 70 years ago among East Poly- Tupaia how navigators waited for seasonal matically by chemically tracing obsidian tools nesia’s Tuamotu atolls, Collerson and Weisler spells of westerly winds to sail east against the to volcanic sources scattered over hundreds turned to more discriminating analyses possi- trade wind direction, Cook presciently sug- and in some cases thousands of kilometers of ble with trace elements and isotopes. The gested that their ancestors had used these west- the Western Pacific (3). results indicate that the adzes came from erlies to sail east into the ocean (2). At about the same time, other researchers five volcanic archipelagoes surrounding the During the 1800s, amateur scholars col- were reconstructing extinct Polynesian voyag- Tuamotus, and to particular islands within lected oral Polynesian migration traditions. The ing canoes and testing them over legendary these, such as Hawai’i’s Kaho’olawe (some they produced were highly suspect, long-distance sailing routes (see the figure) 4000 km to the north-northwest). The authors because they cut and pasted together passages (4), studying traditional navigation on remote do not hesitate to relate this connection to leg- Micronesian and Melanesian islands where ends of canoe voyaging between Hawai’i and voyaging had not died out (5), and using com- Tahiti via the Tuamotus, as well as the 1976 The author is in the Department of , University of Hawai’i, , HI 96822, USA. E-mail: puter simulations to elucidate strategies of voyage over this route of the modern double

CREDIT: FRANK WANDELL CREDIT: [email protected] ocean and island colonization (6). canoe Hokule’a (see the figure) (8).

www.sciencemag.org SCIENCE VOL 317 28 SEPTEMBER 2007 1873 Published by AAAS PERSPECTIVES

6. G. Irwin, J. Polynesian Soc. 98, 167 (1989). Consilience (9) between disparate research need to look for Polynesian basalt adzes there. 7. M. I. Weisler, Ed., Prehistoric Long-Distance Interaction approaches works well in Polynesia (10). References in Oceania: An Interdisciplinary Approach (N. Z. Further integration of chemical sourcing with 1. K. D. Collerson, M. I. Weisler, Science 317, 1907 (2007). Archaeol. Assoc. Monogr. 21, , 1997). other approaches, especially DNA investiga- 2. J. Cook, The Voyage of the Endeavour, 1768–1771, J. C. 8. B. R. Finney, Science 196, 1277 (1977). Beaglehole, Ed. (Hakluyt Society, Cambridge, 1955), pp. 9. E. O. Wilson, Consilience: The Unity of Knowledge (Knopf, tions of Pacific islanders and their plants and 153 and 154n. New York, 1998). animals, looks promising. For example, a bone 3. R. C. Green, Bull. Indo-Pac. Prehist. Assoc. 15, 119 (1996). 10. P. V. Kirch, R. C. Green, Hawaiki, Ancestral Polynesia: An of a Polynesian chicken excavated in Chile has 4. B. R. Finney, in Polynesian Culture : Essays in Essay in Historical Anthropology (Cambridge Univ. Press, Cambridge, 2001). recently provided archaeological support for Honor of K. P. Emory, G. A. Highland et al., Eds. (Bishop Mus. Spec. Publ. 56, Honolulu, 1967), pp. 141–166. 11. A. A. Story et al. Proc. Natl. Acad. Sci. U.S.A. 104, 10335 Polynesians having reached South America 5. D. Lewis, We the Navigators (Univ. of Hawaii Press, (2007). in pre-Columbian times (11). Now we Honolulu, 1972). 10.1126/science.1149035

PHYSICS The surprising effects of adding or subtracting photons from a light beam may yield tools for Quantum Weirdness in the Lab information processing. Robert W. Boyd, Kam Wai Clifford Chan, Malcolm N. O’Sullivan

n ordinary arithmetic, multiplication obeys which the operations are performed. This photon). Row D illustrates the consequence of a commutative law. That is, for any two result is a striking confirmation of the lack first adding a photon to the field and then sub- Inumbers n and m, the product nm is always of commutativity of quantum mechanical tracting a photon, whereas row E illustrates the equal to mn. In classical physics, measure- operators. Moreover, the authors present the situation in which a photon is first subtracted ments of physical properties also obey a com- strongly counterintuitive result that, under and then a photon is added. One sees that the

mutative law. For example, if one first meas- certain conditions, the removal of a photon fields created in these two situations are on August 17, 2009 ures the position of a particle and then its from a light field can lead to an increase in the markedly different. momentum, one obtains the same result by mean number of photons in that light field, as Beyond the conceptual interest in the first measuring the particle’s momentum and predicted earlier (4). then its position. However, quantum mechani- The basic idea of the n = 0.57 cal quantities do not in general obey this com- experiment of Parigi et al. A 0.6 mutation relation (1). In fact, the breakdown and some of their results are 0.4 ) E (

of the commutative law lies at the heart of shown in the figure. In the p 0.2 Laser many fundamental quantum properties, such top row, a laser beam passes th Quantum state 0 www.sciencemag.org as the Heisenberg uncertainty principle. In the through a rotating ground analyzer –2 0 2 example of position and momentum, the lack glass plate (th) to mimic the 0.6 n = 1.1 of commutativity is conventionally stated random fluctuations of a ther- B ^ ^ ^ ^ 0.4 by means of the relation xp – px = ih/2π, mal source and is detected ) E ^ ^ ( wherex andp are the quantum mechanical by a quantum state analyzer p 0.2 a operators (2) associated with position and (QSA). The results of the mea- 0 momentum, respectively, and where h is surement are shown on the –2 0 2

Planck’s constant. right. Here, p(E) gives the pro- Downloaded from In an intriguing and illustrative report on bability distribution of the C 0.6 n = 2.0

) 0.4 page 1890 of this issue, Parigi et al. (3) present electric field amplitude E. E ( p the results of a laboratory demonstration of Rows B through E illustrate a† 0.2 what happens in the quantum mechanical the consequences of acting 0 operations of photon creation and annihi- on the input state by various –2 0 2 lation, which lacks commutativity. These quantum mechanical opera- 0.6 D n = 1.8 authors add a single photon to a light beam, tions. Row B shows the result 0.4 ) E

which corresponds to the action of the stan- of removing a single photon ( p 0.2 dard quantum mechanical creation operator â†. from the field with a beam a† a They can also subtract a single photon from splitter. Counterintuitively, the 0 –2 0 2 the light beam, which corresponds to the anni- mean number of photons n in hilation operator â. the output field is increased E 0.6 n = 2.8 Parigi et al. measure the quantum mechan- by this operation. Row C 0.4 ) SCIENCE E (

ical state of a thermal light field after perform- illustrates the consequence of p 0.2 ing these two operations on it, and they show adding a single photon to the a a† 0 that the final state depends on the order in input state with an optical –2 0 2 parametric amplifier (a device E that splits one photon into two, The authors are at the Institute of Optics, University of Quantum arithmetic. Schematic experimental procedure of Parigi et al. Rochester, Rochester, NY 14627, USA. E-mail: boyd@ each with approximately half and some of their laboratory results. The order in which photons are added

optics.rochester.edu the energy of the original and subtracted from a light field strongly influences the field’s properties. HUEY/ ADAPTED BY P. CREDIT:

1874 28 SEPTEMBER 2007 VOL 317 SCIENCE www.sciencemag.org Published by AAAS