Many historians describe writing a monograph as a ‘journey’ or a ‘voyage’, but far fewer cop to that journey being ‘guided solely by curiosity’. These are Janina Wellmann’s words in the epilogue of Biological Motion (p. 209). And though Whitney Barlow Robles makes no such direct admission, ‘curiosity’, in both its noun and verb forms, is the propulsive force behind Curious Species, in which her own curiosity is as palpable a force as that of the naturalists she reads so closely. To be sure, these books are radically different. Yet they both aim at a synthetic view of the life sciences in Europe and the United States, each through its own distinctive historical lens. Densely detailed, sometimes richly atmospheric, both accounts span centuries, cutting cross-sections through scientific theory and practice. Both books are about the ways in which life – from the animal to the cell to the molecule – acts on the human imagination. Both books look to the past for clues to reclaiming the mystery and vital energy that humans have so often seen in life throughout our history. And both books challenge the notion that science, as much as we value it, should lay sole claim to the task of interpreting life. As Wellmann writes, and Barlow Robles would certainly agree, ‘nature as a scientific object comes to form the borderline between the sciences and the humanities’ (p. 209).

Barlow Robles’s Curious Species blends elements of cultural, intellectual and social history in an account of natural history in the eighteenth century and today that centres four different animal species or taxonomic groups. She begins with coral polyps, and moves to flatfishes and rays, timber rattlesnakes and, finally, raccoons. For each of these, Barlow Robles delves into the archival collections of European and American naturalists, visiting approximately thirty libraries, herbaria and museums around the world, from the Royal Society and the Natural History Museum in London, to American institutions like the Linda Hall Library and the Harvard Museum of Comparative Zoology, and including a handful outside the United States and the United Kingdom (Germany, the Netherlands, Australia). She finds fascinating traces of her focal animals in the archival and natural-history collections of multiple eighteenth-century American and European naturalists, asking how these ‘moving targets of inquiry guide curiosity’s path in fundamental ways’ (p. 2). Many of these figures reappear several times throughout the book, including Dutch botanist Jan Frederik Gronovius, American brothers William and John Bartram and Royal Society fellow John Ellis (to name only a few).

One of Barlow Robles’s aims in these chapters is to enrich our account of Enlightenment science, arguing that although animal collections were converted into objects of natural history and taxonomically subdued by the ‘strong arm of system’, this ‘attempt at disenchantment’ was never fully successful (pp. 18–19). Barlow Robles cites Jessica Riskin and Meghan K. Roberts in her emphasis on the ‘emotion, passion, and sentiment’ that Enlightenment scientists could never quite eliminate, despite their aspirations (p. 9). Alternating with these more traditional historical chapters, Barlow Robles brings the mystery of each non-human animal alive in the present day, recounting her own experiential research: floating above Endeavour Reef in Australia, hunting the secret hibernacula of rattlesnakes in New Hampshire, or holding the hand of an endangered raccoon on the island of Cozumel.

Wellmann’s Biological Motion is even less traditional. Her historical ‘Ariadne’s thread’ is the study of ‘biological motion’ (p. 209). The term was coined only in the 1970s, but it is a phenomenon that she roots in classical Greece and then follows from the seventeenth century to today. She begins by asserting that motion – ‘active and self-directed’ – has, since Aristotle, been the defining quality of life. And yet biological motion has never itself been a focus of sustained scientific or scholarly attention, subsumed always by either physics or the study of animal behaviour (p. 15). Wellmann selects particular ‘sites’ in which the scientific understanding of biological motion made significant shifts, focusing on the ways in which it has been captured, represented and modelled since the seventeenth century (pp. 20–21). From mid-nineteenth-century serial photography, to twenty-first-century silicone microrobots, to the seventeenth-century writings of Dutch microscopist Antoni van Leeuwenhoek (again, to name only a few), Wellmann moves, sometimes non-chronologically, across a landscape of changing perception, philosophy and technology. Her multitude of historical actors, human and otherwise, come alive with her close reading of published primary sources, complemented by detailed endnotes on a range of secondary sources. Relying on scholars like Hannah Landecker and Natasha Myers, Wellmann brings the history of science into conversation with a diversity of disciplines, including art history, the history of visual projection and the history of robotics, and her notes often read like a highly eclectic annotated bibliography.

Despite her wide-ranging interest in scholarly discourse, Wellmann does not seem intent on making a historiographical intervention. Instead, she probes a whole host of binaries that have characterized biological thinking over the past few centuries. Cell/animal, living/non-living, mechanism/vitalism, natural/artificial – all of these and more come under scrutiny. Wellmann examines the ways in which modelling and representing motion have changed as the ‘locus’ of animate motion has ‘migrated from animal to matter, from the organized to the inchoate, from organs of locomotion to contractility of all living matter’, until motion itself ‘became the determining feature and essential explanation of reproduction, physiology, or protein actions’ (p. 24).

Barlow Robles is concerned with some of the same binaries, though her foremost concern is the continued haunting of biology by hierarchy. Originating in the ancient scala naturae, hierarchy persisted, in ways both subtle and obvious, as it was woven into the eighteenth-century taxonomic scheme that still shapes biological categories today. In each section, Barlow Robles finds a story of how non-human animals have presented a multidimensional challenge to human dominance. Corals, for example, generated uncertainty about the line between life and non-life, and between plant and animal. At the same time, these ‘brainless polyps’ also menaced the aspirations – and ships – of explorers and would-be colonists attempting to navigate unfamiliar shorelines. Then, after said settlers had finally made landfall in the New World, they could rely on rattlesnakes to unsettle them, providing a potent symbol of resistance precisely because of the fear and the uncertainty their mysterious habits provoked in Europeans.

Over and again, Barlow Robles’s sources reveal that non-human animals have constrained and shaped natural-historical practices, biological concepts and colonial ideologies. Importantly, however, non-human animals are not the only marginalized historical actors that she seeks to illuminate; in each episode of investigation that she reconstructs, Barlow Robles also seeks the traces of indigenous knowledge and enslaved labour. She reads against the grain, flagging the unseen toil demanded by collecting expeditions and preservation regimens. These tasks were left unspoken, rendered invisible by naturalists who considered both labour and labourer (likely, in the eighteenth century, enslaved) unworthy of scientific acknowledgement. For Barlow Robles, attention to the material culture of natural-history collecting, in the effort its techniques entail, enables a sensitivity to this fuller picture, in which both non-human animals and erstwhile hidden human actors must be given their due.

In fact, in important ways, both Wellmann and Barlow Robles engage in and respond to the material turn in the history of science, carefully considering how the wily subjects and unwieldy substances of biology have co-constituted the intellectual, social and cultural dynamics of scientific practice. For Barlow Robles, this engagement is immersive, and it earns her a flat tyre while chasing Captain Cook’s ghost to Tribulation Bay in far north Queensland, as well as a sliced hand while cutting, flattening and mounting a fish according Gronovius’s (supposedly simple) instructions for collection preservation. For her, material culture and real-life experience help to expose the tacit knowledge and unacknowledged labour hidden by traditional sources.

For Wellmann, materials matter most when they obstruct or enhance the visualization and representation of biological motion. While her prose (translated from the German by Kate Sturge, who also translated Wellmann’s first monograph) can occasionally feel oblique to the point of obscurity, she is at her best when describing the spectacles afforded by microscopic and molecular movements: fluorescent molecular labels on the proteins that climb along muscle fibres, theatrically oversized eighteenth-century solar microscope projections, the contractile viscosity of an amoeba’s protoplasm or, harnessing Leeuwenhoek’s descriptions, the ‘animalcula’ who move beneath the microscope’s lens ‘so quick one after the other that with our Mouths we could not so quickly pronounce one syllable after an other [sic]’ (p. 102). In these moments, the importance of scientists’ efforts to capture and describe the moving stuff of life is abundantly clear.

So much that Wellman describes is experiential and yet we know it only through its inscription, which, in the end, is what counts. For Wellmann, from the time of Descartes, the ‘imitation of movement becomes one with the knowledge of movement’ (p. 38). Leeuwenhoek’s ‘lush’ written descriptions in the seventeenth century are supplanted by long photographic exposures of gastrulating embryos in the nineteenth century, preserving ‘mobile cells as blurred traces’ (p. 156). From these traces, calculations emerge, and data replace mechanism with probabilistic prediction. Today, Wellmann writes, maths is the ‘next microscope’. The resulting statistical distillation of animate motion must then be converted into an animation to be comprehended (p. 203).

Wellmann’s pleasure and disappointment in such animations are evident in equal measure. When animals and cells and even tiny silicone robots dance through space, our eyes ‘attribute movement to them not by noting their statistical patterns, but by ascribing to them the very qualities in which Aristotle once located life’ (p. 208). Animate movement, she argues, is like choreography; an animal moves forward in a pattern that persists, while also incorporating contingent variations. Mathematics translated into animation, to Wellmann’s mind, is no substitute.

Barlow Robles shares Wellmann’s disaffection with the flattening and standardizing impulses of modern biology. From the time of the Enlightenment, she argues, the ‘drive for total and totalizing knowledge of nature’ was always undermined at the edges, where naturalists came ‘up against the limits of their own knowledge’ (p. 6). More than that, there was never any chance of ‘effacing ourselves from our research in the name of objectivity. We cannot escape the animal foundations of human knowledge, not least because we ourselves are never not writing or working or thinking as animals’ (p. 9).

Today, Barlow Robles writes, the mysterious power of animals who, like racoons, ‘don’t fit calmly into archetypes of wild and tame, natural and artificial’, unsettling the boundaries between human and non-human with tactility and curiosity, is only more affecting for us (p. 235). What if we, like them, could ‘exploit the fine line between wildness and tameness’ (p. 224)? She seeks signs of hope in hybrid agents and their disruptions of hierarchy and human agency, in the face of the Anthropocene bearing down on us all. Moreover, Barlow Robles’s book argues, in both form and content, against the modern siloing of scholarly knowledge. In her quest for an experiential understanding of the history of natural history, she invokes the habits of science and nature writers: they are more akin to bees, gathering pollen and nectar from many different sources, than to the single-minded piggishness of foraging historians. Don’t worry, it’s a compliment! And really, she hopes to ‘make a pig fly’, to be ‘strategically undisciplined’, and follow a hybrid methodology (p. 20–1).

Wellmann also raises the spectre of the Anthropocene to argue for a radical reorientation towards disciplinarity. Embracing a ‘new vitalism’, she rejects the way in which twenty-first-century biology has sanitized biological motion to a probabilistic aggregation. Offering an alternative vision, she writes, ‘the living world is an event, new at every instant … not only is it in constant flux, but no disciplinary approach, whether in the natural sciences, the humanities, or the social sciences, can continue to stake an exclusive claim to explain it’ (p. 176).

Historians will find much of value in these books, while also noting the unevenness generated by their non-standard narrative structures. Both are worth a look for scholars interested in considering different modes of historical storytelling. Selective use of chapters and sections from either book would be useful in undergraduate courses, where focused vignettes provide evocative portrayals of scientific history: well-chosen excerpts would be effective demonstrations of the many interdependent material, theoretical and ideological elements that shape scientific theory and practice. This interplay will also be apparent to the general reader who picks up Curious Species, which is likely to have broad appeal not least because of the book’s attractive design and lovely colour plates.