Metals enable a non-enzymatic acetyl CoA pathway

The evolutionary origins of carbon fixation, the biological conversion of CO2to metabolites, remain unclear. Phylogenetics indicates that the AcCoA pathway, the reductive fixation of CO2to acetyl and pyruvate, was a key biosynthetic route used by the Last Universal Common Ancestor (LUCA) to build its biochemistry. However, debate exists over whether CO2fixation is a relatively late invention of pre-LUCA evolution or whether it dates back to prebiotic chemistry. Here we show that zero-valent forms of the transition metals known to act as co-factors in the AcCoA pathway (Fe0, Ni0, Co0) fix CO2on their surface in a manner closely resembling the biological pathway, producing acetate and pyruvate in near mM concentrations following cleavage from the surface. The reaction is robust over a wide range of temperatures and pressures with acetate and pyruvate constituting the major products in solution at 1 bar of CO2and 30 °g;C. The discovered conditions also promote 7 of the 11 steps of the rTCA cycle and amino acid synthesis, providing a stunning direct connection between simple inorganic chemistry and ancient CO2-fixation pathways. The results strongly sup-port the notion that CO2-fixation pathways are an outgrowth of spontaneous geochemistry.

On the Late Invention of the Stereoscope

It was not until 1838, when Wheatstone published his account of the stereoscope, that stereoscopic depth perception entered into the body of binocular phenomena. It is argued that the stereoscope was not invented earlier because the phenomenon of stereopsis based on disparity had not been adequately described. This was the case despite the fact that there had been earlier descriptions of tasks that could be performed better with two eyes than with one; the perceptual deficits attendant upon the loss of one eye had been remarked upon; analyses of the projections to each eye were commonplace, and binocular disparities were accurately illustrated; moreover, binocular microscopes and telescopes had been made over a century earlier. Theories of binocular vision were generally confined to accounting for singleness of vision with two eyes, and the concepts employed to account for this were visible direction, corresponding retinal points, and union in the brain. The application of these concepts inhibited any consideration of disparities, other than for yielding diplopia. When perception of the third dimension was addressed by Berkeley at the beginning of the eighteenth century, it was in the context of monocular vision and binocular convergence. Thereafter visual direction became the province for binocular vision and it was analysed in terms of geometrical optics, whereas visual distance was examined in the context of learned associations between vision and touch. This artificial division was challenged initially with respect to visual direction and later with respect to stereopsis. An additional factor delaying the invention of the stereoscope was that experiments on binocular vision generally involved abnormal convergence on extended objects. Wheatstone's accidental observation of stereopsis was under artificial conditions in which disparity alone defined the binocular depth perceived. Once invented the stereoscope was enthusiastically embraced by students of vision. It is suggested that the ease with which retinal disparity could be manipulated in stereopairs has led to an exaggeration of its importance in space perception.

Towards a Less Orthodox History of Hausaland

The historiography of Hausaland has laboured under a strong tradition of orthodoxy which recent secondary works have inherited from the more-or-less primary oral-cum-written sources. General cultural evidence (linguistic, ethnographic and archaeological) has been regarded as subsidiary, so that its potential for reconceptualization and for critical reevaluation of the conventional sources and orthodox interpretations has been missed. Instead, antiquarian approaches have been encouraged. Thus the view has persisted that Hausa as a cultural and linguistic entity has an antiquity running to several millennia, and also that it originated in the Sahara or around Aïr, whence it was pushed southward by desiccation or by Tuareg nomads. Contrarily, the clear message of linguistic geography and of Hausa's place within the Chadic family is that Hausa. expanded from east to west across the savanna belt of northern Nigeria. And the relative homogeneity of the language and culture within this vast zone indicates that the spread is quite recent (within the present millennium, say). It would have involved some assimilation, of previously settled peoples of the northern Nigerian plains, most of whom wouldl have spoken languages of the ‘Plateau’ division of Greenberg's Benue–Congo subfamily, of Niger-Congo.This Hausaization, as it proceeded from its old bases in eastern Hausaland, would have been both a cultural and an ecological process, through which woodland would have been converted into more open and continuous savanna to support grain-cultivation and a denser peasant population. This process would have reached western Hausaland (Zamfara and Kebbi) around the middle of this millennium. Cattle – and Fulani herdsmen – would in time have played an important role in this cultural ecology (and in restricting the tsetse zones).The old theory of a northern origin for the Hausa is bound up with the problem of Gobir in north-western Hausaland. Gobir's claim to be one of the original seven kingdoms (Hausa bakwai) is probably a late invention. Moreover, the common assumption that Gobirawa Hausa migrated from Aïr seems to derive from a misinterpretation of the written sources.Finally the bakwai legends are reconsidered. Despite the scepticism of some modern critics, the legends appear to reflect, albeit in idealized form, a real historical development. They represent a foundation charter for the Hausa as a multi-state ethnicity, and enshrine the vague memory of how Hausaland and ‘Hausaness’ began from a series of small centres and hill-bases on its eastern side. Thus the interesting argument of Abdullahi Smith, that the Hausa people emerged long before state systems arose among them, is disputed. Rather, these should be seen as two facets of a single process during the present millennium.

Of the antiquity of the Transfusion of bloud from one animal to another

There hath been of late some contest about the Origin of the Transfusion , the English first claiming it as a late Invention of theirs; the French pretending thereupon, that it had been proposed among them ten years agoe: after which, it was affirm'd upon further investigation, by some ingenious persons in England , that there it had been known 30 years agoe; whereof the Publisher of these Tracts hath good proof in his hands.