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time happens during footprint formation, year for a healthy vegetarian diet, only In the footsteps very -like tracks would be formed. about 60 per cent of the present land In the case of the Taylor trackway, howev­ under cultivation would be needed to feed of ? er, the toe impressions apparently did not the world population. With the further SIR-It is impossible to work on collapse. Weathering of the rock surface modernization of techniques in develop­ 2 footprints in Texas'· , without becoming has resulted in the development of more ing countries, that 60 per cent would be involved in the "man track" controversy. I or less non-impressed or irregularly im­ more than sufficient to feed the projected have seen most of the alleged human pressed, coloured toe marks and a larger world population in the next century. This ichnites, but have been reluctant to pub­ track outline associated with the more would not only stop the deforestation that lish interpretations without a thorough deeply impressed, originally discovered contributes substantially to the increase in 4 understanding of the details of formation "man tracks" • Although unusual, the atmospheric CO,, but would enable us to of unquestioned dinosaur tracks, and the phenomenon is not "unprecedented," as reforest 40 per cent of the present agricul­ gaits of the trackmakers. Now Kuban and Morrison states; an ornithopod trail with tural land, leading to large-scale absorp­ Hastings have sparked a revival of interest footprints delimited mainly by such colour tion of atmospheric CO,. Such an exten­ in this topic with their publications on the distinctions occurs in the Dakota Group sive mopping-up of carbon dioxide by "colour distinction" of the Palauxy River (Cretaceous) along the Alameda Parkway young growing forests may be the only "man tracks"' ... I am prompted to alter my near Denver, and some of the sauropod way to prevent the worrying consequ­ approach to this matter by John D. Mor­ footprints from the Purgatory River (Mor­ ences of the greenhouse effect, at least ris's recent letter to Nature'. rison Formation, Jurassic) of Colorado until alternative energy sources can effec­ Most of the structures identified as are distinguishable from the surrounding tively replace fossil fuels. "man tracks" in Lower Cretaceous rocks rock mainly by their colour (M.G. Lock­ Legislation to effect a change in our die­ at Glen Rose and elsewhere in Texas are ley, personal communication). tary habits may be difficult to achieve. But not footprints of any kind, let alone hu­ The origin of such colour-delimited fortunately, it is a step that we could fruit­ man tracks, but are simply solution fea­ footprints was much discussed by partici­ fully take at the individual level without tures and/or scour marks of the kind that pants on the field trip of the recent First having to wait for government action, the can be seen in riverbeds throughout cen­ International Symposium on Dinosaur laws of supply and demand would go a tral Texas, and even on exposed rock sur­ Tracks and Traces (Albuquerque, May long way towards making sure that re­ faces well away from river valley. Some of 1986). The tracks were perhaps filled with duced meat demands would decrease the the "man tracks" do occur in good track­ sediment of a contrasting type from that in pressure on land and pave the way for ways, however, and clearly represent the which the footprints were impressed; this rapid afforestation. footprints of bipedal animals. The Taylor inhomogeneity may have led to the colour T.R. VIOYASAGAR trackway, featured in much of the crea­ distinctions in response to modern weath­ Max-Planck Institute for tionist literature, is a good example, and I ering. Alternatively, as dinosaurs crossed Biophysical Chemistry, have examined a similar trail in Hondo mud flats, their weight may have squeezed D-3400 Gottingen, West Germany Creek, Bandera County. The footprints in pore water from the sediments beneath these trackways are generally elongated their feet, resulting in subtle chemical dif­ depressions rather lacking in detailed ferences from the surrounding sediments; Damadian defended morphology. If one looks at enough bipe­ the coloured tracks may thus have formed SIR-It is disturbing that you should pub­ dal dinosaur footprints, at enough sites in as "ghost tracks" some distance below the lish such a prejudiced review (Nature 320, Texas, it is possible to find footprints in­ sediment/water interface. 318; 1986) of Sonny Kleinfield's book, A termediate in shape between the elongate JAMESO. FARLOW Machine Called Indomitable, containing depressions of the "human" trackways Department of and Space Sciences, derogatory remarks about Raymond and more normal tridactyl footprints of Indiana University-Purdue Damadian, whose struggles have given typical bipedal dinosaur trails. University, at Fort Wayne, the world a powerful tool for medical di­ I have measured stride, pace and foot­ Fort Wayne, Indiana 46805 USA agnosis. The reference to Damadian as a print lengths of over 70 bipedal dinosaur 1. Farlow, J.O. Nature 294,747-748 (1981). "misfit" does harm to a journal with a 2. Farlow, 1.0., Hawthorne, J.M. & Langston, W. in First trails in Texas, and supplemented these International Symposium on Dinosaur Tracks and Traces, reputation for even-handedness and fair data with measurements from the litera­ Abstracts with Programs (ed. Gillette, D.D.) 14 (New Mex­ play. In his review Peter Newmark seems ture of more than 650 additional bipedal ico Museum of Natural History. Albuquerque, 1986). Origins Res. to take popular acceptance as the sole cri­ 2 3. Kuban, G.J. 9, 1-71,7-13 (1986). dinosaur trails ; the "human" trails match 4. Kuban, G .J. in First International Symposium on Dinosaur terion for scientific excellence. If this were typical dinosaur trails in the relationship Tracks and Traces, 17 (New Mexico Museum of Natural true, Copernicus, Lavoisier, Darwin, History, Albuquerque, 1986). between footprint size and pace or stride 5. Morris, J.D. Nature 321,722 (1986). Planck and Einstein were all "misfits", length, and also show similar step angles. 6. Cole, J.R. & Godfrey, L.R. (eds) The Paluxy River Foot­ rejected by their contemporary peers. print Mystery-Solved, Creation/ 5(1): 1-56, 1985. Thus even before the "colour distinctions" 7. Farlow, J.O. Annotations to Bird, R.T. Bones for Barnum Newmark's comment that I, though were recognized, there was ample reason Brown: Advenlures of a Dinosaur Hunter (ed. V.Y. Schrei­ successful in casting a spell over Dama­ for regarding the Paluxy River "human" ber) (Texas Christian University Press, Fort Worth, 1985). 8. Thulborn, R.A. & Wade, M. Mem. Queens/. Mus. 21,413- dian, nevertheless "remain a voice in the trackways as the poor end of the impres­ 417. wilderness", is also uncalled for. I suggest sion/preservation spectrum of theropod or he reads the review (Nature 311, 682; 6 7 ornithopod trails • • 1984) of my book, In Search of the Physi­ Kuban corroborates this interpretation Greenhouse cure cal Basis of Life, where the reviewer, by making a good case• that many of the SIR-Those who are concerned about the Dick, though a long-time scientific oppo­ "humanoid" footprints were formed by consequences of the "greenhouse effect" nent of mine, stated with fairness and bipedal dinosaurs walking in an unusual, overlook the benefits that would follow general accuracy: "Since the 1950s major­ "flat-footed" fashion, with their metatar­ from the general adoption of a vegetarian ity views of the cell have moved signifi­ sals pressed against the substrate. Similar diet. If there were a halt to the consump­ cantly nearer to those of Dr Ling ... ". metatarsal tracks have been reported tion of grain-fed livestock products (while GILBERT N. LING 8 from a Cretaceous site in Queensland , retaining the present pasture lands to sup­ Department of Molecular Biology, and perhaps elsewhere. If the toe marks of port animals for meat and milk), at a per Pennsylvania Hospital, Philadelphia, such footprints were to collapse, as some- capita grain consumption of 200 kg per Pennsylvania 19107, USA

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