One of the first to realize the phenomenon was Max Rubner when he studied in 1883 the basal metabolism of dogs with different sizes. Rubner proposed that the cause of the phenomenon was the heat that was lost through the skin. Since the surface of the skin varies with the square of the size of the animal, while its volume varies with the cube, this would imply that the basal metabolism B varies proportionally to the mass raised to 2/3, M2 / 3. However, in 1932, measurements made by his namesake Max Kleiber in mammals over a larger mass range, including oxen and rats, seemed to indicate that metabolism actually varied according to M3 / 4, a relationship we know today as the law of Kleiber. The search for an explanation for this exponent opened an intense debate for decades, which seemed to conclude in 1997 with the fractal model of Geoffrey West and colleagues.

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This model justified the exponent by the Poland B2B Email Lists fractal shape of the resource distribution networks in organisms, such as the circulatory or respiratory systems. Measuring the basal rate in organisms is a delicate and time consuming experimental task. As metabolic measurements increased in more animals, the fractal model began to show more and more discrepancies. Thus, in some animal groups such as small birds or insects, the exponent 3/4 does not fit. And even in mammals, for which Kleiber’s law was conceived, the data show a notable divergence from the theoretical law. Now the authors of an article recently published in Scientific Reports, (the open access of Nature), Fernando J. Ballesteros and Vicent J. Martínez ( Astronomical Observatory of the Universitat de València-Parc Científic ), Bartolo Luque ( ETSI Aeronáutica y del

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Espacio of the Polytechnic University of Madrid ), Lucas Lacasa (School of Mathemtical Sciences of the Queen Mary University of London ), Enric Valor (Department of Thermodynamics of the University of Valencia) and Andrés Moya (Institute of Integrative and Systems Biology-UV / CSIC in the Science Park), have found the piece that completes the puzzle from a theoretical model of Astrophysics. “During the writing of the book ‘Fractals and Chaos’, in which we talked about Kleiber’s law, we realized that the fractal model of West and colleagues did not fit. The thermal explanation seemed more natural, but it was necessary to take into account the energy part that is not dissipated as heat ”, says Fernando Ballesteros. “Vicent and I plugged this into the thermal model and saw that the data fit perfectly with our theory.

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