“There have been many studies over the decades why people of Polynesian ancestry have increased body mass. These studies have focused on the idea that increased body size provided a survival advantage during the complex colonizing voyages.

“One previous, but now debunked, theory was the ‘thrifty gene hypothesis’, which is unsupportable in the light of the knowledge that the migratory voyages were planned, not accidental, voyages to new islands.

“Here, Montenegro and colleagues investigated the idea that increased body size gave an advantage in dealing with the cold during voyages. They compared the energy cost between voyages from Tahiti to each of Hawaii and the North East coast of Te Ika a Māui of Aoteaora NZ. This was done by complex mathematical modeling.

“Using ‘morphological data from Polynesian populations,’ researchers found that a trip from Tahiti to Aotearoa NZ in January/ February would require up to an extra 1,500 calories per day for thermoregulation. However the amount of extra calories needed for the trip decreased when weight (muscle mass and subcutaneous fat) was increased in their models, with similar calorie requirements as for the trip to Hawaii. They predicted that women would have a greater advantage in thermoregulation than men.

“The authors concluded that these physiological features may have helped surviving voyaging to Aotearoa NZ. This may or may not be true. If true, it will likely be only one of multiple factors in why Polynesian people have increased body size. If true, it is important to stress than major genetic selection on increased body size would have happened during the settlement of Western Polynesia and not necessarily in the settling of Aotearoa NZ – I wondered why the authors did not apply their modeling to the Lapita migration through the Bismarck Archipelago to Samoa and Tonga.

“More definitive answers to this question will come in the next few years. If a larger body size made the ancestors of Polynesian people more likely to survive long voyages, we would expect to see more genes associated with larger bodies in modern Polynesian populations. While the well-studied Pacific-specific CREBRF variant is related to body size, other body-size genes have not yet been identified. There is also no robust evidence showing that the CREBRF variant was specifically favored and passed down through generations in the past because it was advantageous. Even if there were, the reasons for selection would remain unknown. It could be thermoregulation and/or resistance to infectious disease and/or adaptation to food sources and/or other factors; very difficult, if not impossible, to determine.

It seems scientists are still extremely fascinated about why Pacific people including Māori have bigger bodies than European counterparts. Unfortunately all the modelling in the world regarding voyages etc. will never answer the question of whether these voyages were the selection pressure that is responsible for this. The authors wildly exaggerate the conclusions they can draw from this data. They state that if the voyagers relied solely on their energy reserves in the form of fat, voyagers would use 107.2 g of fat per day, or an extra 2.68 kg at the end of a 25-day trip. What significance does 2.68 kg hold? Is this enough of a deficit that then explains why these people were successful in their voyages?

A minor comment would be why did they calculate the energy balance deficit based on a migration from Tahiti to New Zealand. I believe Matauranga Māori indicates that the voyages to Aotearoa were centred in the Cook Islands some 1000 kms further West than Tahiti. Further to this the authors have not carried out any consultation with Māori with regards to this research. Instead in the acknowledgements they refer to conversations with OLaGa research group which is a group of tauiwi scientists that are studying the biological determinates of lipids in Samoans. The voyages the authors refer to in this manuscript however concern Māori and I am confident that Matauranga Māori would be important for the narrative presented.

Statements like “while the number of people that perished in colonizing Polynesia is unknown, it is likely that there were many failed voyages resulting from storms, loss of bearings, depletion of provisions,and other factors” are colonial and undermine the Indigenous knowledge that contributed to these great voyages. I hope we can move away from this kind of science, which does nothing to benefit the populations and people that are the subjects of these studies.

Alvaro Montenegro and colleagues – a collection of North American researchers plus Aoteroa’s own Atholl Anderson – have tried to model the energetic demands of our Polynesian ancestors who settled the cooler Eastern Polynesian islands. Based on equations and lots of assumptions about what our ancestors may have worn and consumed, how wet they got and how much sun and wind they were exposed to, they conclude that the energetic demands required to arrive alive in Aotearoa would have been substantially higher the energetic demands required to reach Hawai’i. This seems reasonable enough. However drawing on the thifty gene hypothesis, they argue that big people with relatively short limbs would have been more likely to survive the migrations across the Pacific because of superior thermoregulatory capacities, thus explaining why Samoans are larger than other tropical Islanders. I might be more inclined to accept their ideas if they had backed them up with any data demonstrating Māori were the biggest of all of the East Polynesians, given the extra thermoregulatory demands required to get here, but no such luck.