Why no bow in Australia? George 2024 study

Indigenous Australians did not make bows, although the peoples of the islands to the north, with whom they traded, used them, and the author, a botanist at Curtin University in Perth, asks whether the reason might lie in the continent's woods. He gathered from public sources three properties of 431 samples of dry wood from 326 species, 106 of them Australian: modulus of rupture (how much load it takes in bending before breaking), modulus of elasticity (how stiff it is) and density, plus the ratio of rupture to stiffness that bowyers use as an index.

Using principal component analysis, he laid the woods out on a two-axis plot that accounts for more than 90% of the variation. Woods known to be excellent for self-bows (Osage orange and two species of yew, 9 samples) and those in common use (maple, hickory, ash, oak, elm, mulberry, black locust and Borassus palm, 44 samples) cluster in the same area: a high ratio of tensile strength to stiffness, and moderate absolute values. Almost all the Australian woods sit elsewhere, strong and dense but stiff relative to what they can take in tension, and so more prone to breaking on the back of the bow.

Some Australian species do fall in the area of the good woods, such as Allocasuarina fraseriana, Intsia bijuga and several eucalypts. Of the species that bowyers on the OzBow forum describe as suitable, however, only Eucalyptus macrorhyncha sits close to the good woods. The roughly 7,000 posts on the subject written between 2005 and 2023 suggest that bows can be made from these woods, but only with carefully chosen staves, often a backing, and long, wide limbs in the style bowyers call Andaman-Holmegaard.

The data come from five public sources, including the US Forest Service wood handbook, a handbook of Australian timbers and the Wood Database website, always for wood at 12% moisture. Values range from 22 to 213 MPa for modulus of rupture (mean 106), from 3,400 to 28,000 MPa for modulus of elasticity and from 0.24 to 1.4 g/cm³ for density. About a quarter of the samples are replicates of the same species. The species were split into four groups: high quality, secondary, other (non-Australian woods whose suitability is unknown, 251 samples) and Australian (127 samples).

The analysis, run in R on centred and scaled variables, uses modulus of rupture, modulus of elasticity, their ratio multiplied by 100, and density. To see how much variation within a species matters, the author randomly split the replicates into two sets twenty times and compared them: a species varies by up to 30% in its properties and by up to 15% in its position on the plot. The qualitative part comes from the OzBow forum, the busiest gathering place for Australian traditional bowyers: the author searched for posts on self-bows and native woods, then searched for each species mentioned by name. Since forum users tend to give common names, species were inferred, and doubtful cases were left out.

No bow was built or tested. The classification of "good" woods comes from bowyers' tradition, not from a measure of performance, and the author himself acknowledges that a wood's suitability for bows is subjective and continuous. Data quality cannot be checked, most species are represented by a single sample, and the 106 Australian species are a small fraction of those on the continent; data are missing for some of the very species bowyers report using successfully. Modulus of rupture describes the breaking load in a single test, not the repeated bending a bow goes through on every shot, and properties closer to actual use, such as work to maximum load, were not considered.

The qualitative part relies on anonymous posts, with species inferred from common names. The link with the absence of the bow in Australia remains a hypothesis: the study suggests that common Australian woods are less favourable, not that this was the cause, and alternative historical and cultural explanations are not tested.

For target archers the study matters little, since it concerns self-bows made from a single piece of wood, not laminated or carbon recurves. For anyone who shoots historical bows or makes their own, it gives a clear account of something bowyers know from experience: the right wood is neither the strongest nor the densest, but the one that takes a lot of tension relative to its stiffness, with middling absolute values. This is also why yew and Osage orange are treated as benchmarks.

The analysis plot, with the data published as supplementary material, shows where a little-known wood falls relative to proven ones, but only as a clue: a species varies by up to 30% from one sample to another, and the stave in hand matters as much as the species. That unfavourable woods call for longer, wider limbs or a backing is bowyers' experience as reported by the author, not a measured result.