In this paper, we provide an analysis of uniqueness; one that sheds light on the nature and role of uniqueness attributions in the life sciences. Though there are metaphysical issues in the neighborhood, we focus on the epistemological implications of uniqueness attributions. More specifically, our attention focuses on unique trait attributions. Unique traits are non-recurrent and as such, limit researcher abilities to acquire evidence, test hypotheses and provide explanations concerning them. Kronfeldner M (2018) What’s Left of Human Nature? A Post-Essentialist, Pluralist and Interactive Account of a Contested Concept. The MIT Press, Cambridge, MA This puts us in a position to draw on the case studies and argue against pessimism more forcefully. This we undertake the next section. In the one following, we consider cases of ‘apparent uniqueness’ before concluding. Radical pessimism

Not shared by any other event, apart from spatiotemporal location and self identity (or it is unknowable whether they are shared by other events). OrWong TW (2019) The evolutionary contingency thesis and evolutionary idiosyncrasies. Biol Philos 34(2):22. https://doi.org/10.1007/s10539-019-9684-0 McConwell AK (2019) Contingency’s causality and structural diversity. Biol Philos 34:26. https://doi.org/10.1007/s10539-019-9679-x Brown P, Sutikna T, Morwood MJ, Soejono RP, Saptomo EW, Due RA (2004) A new small-bodied hominin from the Late Pleistocene of Flores. Indonesia Nature 431(7012):1055 I got a new one from the Crocodile on the banks of the great grey-green, greasy Limpopo River,’ said the Elephant’s Child. ‘I asked him what he had for dinner, and he gave me this to keep.’

Uniqueness has received little attention in recent philosophy of science. This is surprising given its important role in the life sciences. There it is often claimed that events, traits, or lineages are unique; for example, that evolutionary events are contingent (McConwell 2019, Currie 2018), irreversible (Maynard-Smith & Szathmary, 1995) or idiosyncratic (Wong 2019); that human beings evolve under unique cultural circumstances (Henrich 2015); and that lineages bear unique, novel traits (Wagner 2014). The metaphysics of evolutionary kinds further suggests an important role for uniqueness. The dominant view understands such kinds as individuals: particular trajectories deserving of narrative explanation (Hull 1976). Powell R (2007) Is Convergence more than an analogy? homoplasy and its implications for macroevolutionary predictability. Biol Philos 22:565–578 urn:lcp:howelephantgotit0000rich:epub:8ea4189d-6f90-49cf-98c5-37d2b0b3a880 Foldoutcount 0 Identifier howelephantgotit0000rich Identifier-ark ark:/13960/t5s877b1k Invoice 1652 Isbn 0805066993 Lccn 2002007216 Ocr tesseract 5.0.0-alpha-20201231-10-g1236 Ocr_detected_lang en Ocr_detected_lang_conf 1.0000 Ocr_detected_script Latin Ocr_detected_script_conf 0.9014 Ocr_module_version 0.0.13 Ocr_parameters -l eng Old_pallet IA-NS-0000798 Openlibrary_edition At the end of the third day a fly stung him on his shoulder, and before he knew it he lifted up his trunk and hit that fly dead. Vantage one. Then the Elephant’s Child felt his legs slipping, and he said through his nose, which was now nearly five feet long, ‘This is too butch for be!’Milam EL (2019) Creatures of Cain: The Hunt for Human Nature in Cold War America. Princeton University Press, Princeton We have no extant relatives which are suspected of sharing similar selective regimes and that can therefore be used to test the fitness consequences of the supposed adaptations. If all or most of the estimated dozen or so extinct hominid species (comprising, perhaps two or three genera) still existed, phylogenetic studies would certainly be easier and might well be useful for distinguishing between competing hypotheses about the spread and maintenance of phenotypic traits of interest. Unfortunately for testing adaptive hypotheses in humans, all the other hominids are extinct and so comparisons between the groups, with special attention to the fitness consequences of differences in key traits, are impossible (Kaplan 2002, 300).

I think, said the Crocodile—and he said it between his teeth, like this—’I think to-day I will begin with Elephant’s Child!’ Wong TW (2020) Evolutionary contingency as non-trivial objective probability: Biological evitability and evolutionary trajectories. Stud Hist Philos Sci Part c: Stud Hist Philos Biol Biomed Sci 81:101246. https://doi.org/10.1016/j.shpsc.2019.101246 The Crab that Played with the Sea – explains the ebb and flow of the tides, as well as how the crab changed from a huge animal into a small one. One theory goes that, by gathering food while the mouth focuses on chewing, it enables the ingestion of the disproportionately large volumes of food required by bigger animals.

So how did the elephant get its trunk?

The elephant's trunk might even have started out as a snorkel in a semi-aquatic ancestor. This seems more plausible when you consider that elephants’ closest living relatives are the fully-aquatic manatees and dugongs. On this functional notion, meerkat teaching shows up as being surprisingly similar to human teaching; scorpion hunting being the prime example. Meerkat ‘helpers’ provision their young with scorpions in distinct stages—dead, stingless and fully functional—in a way that is indexed to the learner’s age (Thornton and McAuliffe, 2006; 2008). This allows the inexperienced to learn the subtle art of scorpion-dispatching in stages. Such teaching fits the functional schematic: if one wants to eat a scorpion, biting off its stinger and passing it to a young meerkat is not beneficial to the helper (the first requirement) and a slow, staged introduction to the dangerous business certainly increases the chances of the novice to learn how to perform it (the second requirement). Bear in mind that till that very week, and day, and hour, and minute, the elephant’s child had never seen a crocodile. And finally he asked an unknown creature (the crocodile himself) the question which he hoped to finally relieve himself of, “What does the crocodile have for dinner?” Then that bad Elephant’s Child spanked all his dear families for a long time, till they were very warm and greatly astonished. He pulled out his tall Ostrich aunt’s tail-feathers; and he caught his tall uncle, the Giraffe, by the hind-leg, and dragged him through a thorn-bush; and he shouted at his broad aunt, the Hippopotamus, and blew bubbles into her ear when she was sleeping in the water after meals; but he never let any one touch Kolokolo Bird. Scuse me,’ said the Elephant’s Child most politely, ‘but do you happen to have seen a Crocodile in these promiscuous parts?’

Wagner GP (2014) Homology, genes, and evolutionary innovation. Princeton University Press, Princeton Unlike researchers who study dinosaurs and have to rely on distant living relatives, such as crocodiles and birds for indirect comparison, students of Proboscidea are fortunate to have living models with which to compare and contrast the extinct taxa directly. This advantage should not be underestimated, because knowledge of the living species helps one to interpret observations of extinct forms and vice versa (Shoshani et al. 1998, 487) Pretorius Y, de Boer WF, Kortekaas K, van Wijngaarden M, Grant RC, Kohi EM, Mwakiwa E, Slotow R, Prins HH (2016) Why elephant have trunks and giraffe long tongues: how plants shape large herbivore mouth morphology. Acta Zoologica 97(2):246–254 Pessimists make a claim about epistemic power and a claim about pursuit: if one targets unique traits, one won’t make much epistemic progress and therefore investigations of unique traits will be fruitless. Both claims are mistaken.Importantly, we further break down evolutionary similarity into two distinct criteria, each of which furnishes a characterization of uniqueness. The first, similarity in selection regimes highlights how shared selection pressures can generate similar traits. On this criterion, uniqueness is equated with being a statistical outlier: traits at an extreme end of a statistical distribution that result from severe and/or persistent selection regimes. The second, evolvability similarity, groups together traits on the basis of dispositional tendencies of lineages to evolve in similar ways. Here, unique traits are the result of path-dependent cascades. Briefly, one can understand a ‘path-dependent cascade’ using machinery developed in the contingency literature. Desjardins ( 2011a, b) defines path dependence as holding when an outcome is probabilistically dependent on the occurrence (or non-occurrence) of specific events along a causal pathway, which he distinguishes from dependence on initial conditions. For the latter, where one begins matters, for the former, what happens along the way matters. A trait is the result of a path-dependent cascade when an evolutionary trajectory diverges from relevant contrasts in exploring a different region of evolutionary space as a result of specific events along its evolutionary pathway. At a first pass, calling a lineage ‘unique’ seems either trivial or confused. According to evolutionary systematics, every lineage is the result of a unique branching event. And yet at the same time, every lineage traces its ancestry to a common ancestor. Does this mean that all lineages are unique? That no known lineages are? If the former, uniqueness attributions are uninformative, simply restating results from systematics; if the latter, such attributions seem spooky, suggesting unique events fall outside the remit of contemporary scientific understanding. This sets up a challenge for any account of biological uniqueness: identify notions which are neither trivial or uninformative, nor confused or spooky. Best elephant gifts: 7 elephant-themed present ideas you can’t resist So how did the elephant get its trunk? Boyd R, Richerson PJ (1985) Culture and the Evolutionary Process. University of Chicago Press, Chicago Rietveld E (2012) Bodily intentionality and social affordances in context. In F Paglieri (ed.) Consciousness in Interaction. The role of the natural and social context in shaping consciousness. Amsterdam: John Benjamin.