Jean Chaline

Phyletic gradualism in a European Plio-Pleistocene Mimomys lineage (Arvicolidae, Rodentia)

The European Plio-Pleistocene Mimomys ( Hintonia ) occitanus-ostramosensis lineage of arvicolid rodents appears to present a genuine case of gradual evolution. Analysis of numerous dental samples recorded from 3 to 1.5 ma by several biometrical methods led to the following conclusions: samples from the whole geographical area order into a morphological continuum (chronomorphocline); the successive populations in the trend show important overlap of their variation; and the absence of stasis or any interruption in the trend, combined with its unidirectionality, suggests genuine phyletic gradualism. The chronomorphocline is characterized by an important increase in tooth hypsodonty, by the progressive and continuous development of lateral enamel tracks. Four phases of evolution can be recognized in the lineage, the rates of morphological changes being variable and related to climatic fluctuations (Reuverian, Pretiglian, Tiglian, Eburonian). Morphological changes are initiated by environmental fluctuations, although the polarity of climatic change is not a determining factor. Environmental changes act as stimulus and release drift processes. Phyletic gradualism occurring over such a wide area implies extensive gene flow, and suggests that only general, not local, environmental components act to produce the observed morphological changes.

The last glacial/interglacial record of rodent remains from the Gigny karst sequence in the French Jura used for palaeoclimatic and palaeoecological reconstructions

Abstract A multidisciplinary approach has produced an exceptional chronological log of climatic patterns for the Upper Pleistocene sequence of Gigny Cave (Jura, France) covering the Pre-Eemian, Eemian Interglacial, Middle Glacial and Upper Pleniglacial, as well as a part of the Holocene. Multivariate analysis (correspondence and component analysis) of rodent associations from the sequence is used here to characterize the different climatic stages in terms of relative temperature, plant cover and moisture. Faunal analysis establishes: (1) positive and negative correlations among the variations of the different species; (2) the significance of axis 1 (component analysis) which, in terms of temperature, opposes cold environments with contrasted continental biotopes; (3a) the significance of axis 2 (component analysis), which reflects vegetation patterns ranging from open to closed habitats; (3b) the significance of axis 3 (component analysis), which expresses trends in moisture; (4) various correlations between faunal and climatic parameters (temperature, plant cover and moisture); (5) evaluation of faunal diversity (Shannon index ranging from 0.74 to 2.27) showing that diversity increases with temperature and the complexity of vegetation, but is not sensitive to moisture. Lastly, the comparison of multivariate methods with the weighted semi-quantitative Hokr method shows the complementarity of the two approaches, the first methods quantifying climatic parameters while the second seems to provide more precise evaluations of the main seasons of rainfall.

Montousse 5 (Hautes-Pyrenees), un nouveau remplissage de fissure a faune de vertebres du Pleistocene inferieur

Resume La faune de Montousse 5, qui renferme a ce jour 68 especes, est un ensemble jusquici inconnu en Europe occidentale, et surtout riche en Vertebres de petite et moyenne taille. La microfaune de Mammiferes se correle avec celle dOsztramos 3 (Hongrie), que lon peut dater de la fin du Villafranchien moyen. Elle semble indiquer le passage dune phase froide a une phase chaude, a la fin du Tiglien.

On the Fractal Structure of Evolutionary Trees

We analyse in terms of a fractal tree the time sequences of major evolutionary leaps at various scales: from the scale of the “global” tree of life (appearance of life to homeothermy), to the distinct scales of organization of clades, such as sauropod and theropod dinosaurs, North American equids, rodents, primates including hominids, and echinoderms. We also apply this type of model to the acceleration observed in the economic crisis/no-crisis pattern in Western and pre-Columbian civilizations. In each case we find that these data are consistent with a log-periodic law of acceleration or deceleration, to a high level of statistical significance. Such a law is characterized by a critical epoch of convergence Tcspecific to the lineage under consideration. These results support a description of evolutionary trees in terms of critical phenomena.

Organ xenografting between rodents: an evolutionary perspective

Rejection times of heart xenografts in several donor-recipient combinations including the guinea pig, rat, hamster, and mouse are examined in light of the paleontological history of rodents and the resulting phylogenetic distances between taxa. This multidisciplinary review at the molecular, chromosomal and morphological levels suggests that xenograft rejection time is inversely proportional to the time divergence or phylogenetic distance, and that the binomial terminology concordant/discordant does not reflect the amplitude of phylogenetic distances.

L'arbre de la vie a-t-il une structure fractale?

Abstract We analyse the time sequences of major evolutionary leaps at various scales, from the scale of the global tree of life, to the scales of orders and families such as sauropod dinosaurs, North American fossil Equidae, rodents, and primates including the Hominidae. In each case we find that these data are consistent with a log- periodic law to high level of statistical significance. Such a law is characterized by a critical epoch of convergence Tc specific to the lineage under consideration and that can be interpreted as the end of that lineages capacity to evolve.

La notion d'espace morphologique,outil d'analyse de la morphodiversité des organismes

Resume Lanalyse de la morphologie des organismes est une base essentielle dans la mise en evidence des changementsevolutifs. La morphologie est maintenant frequemment abordee par des procedures quantitatives, dont certaines permettent de construire de veritables cartes morphologiques ou les dissemblances et ressemblances de formes entre les organismes sont directement lisibles et quantifiees. La notion despace morphologique, illustree ici par differents exemples, se revele particulierement feconde pour comprendre comment la diversite morphologique dun ensemble dorganismes (stades ontogenetiques, populations, clades) se structure, et par consequent pour interpreter en termes evolutifs ou adaptatifs des changements de formes.

Développement humain et loi log-périodique

We suggest applying the log-periodic law formerly used to describe various crisis phenomena, in biology (evolutionary leaps), inorganic systems (earthquakes), societies and economy (economic crisis, market crashes) to the various steps of human ontogeny. We find a statistically significant agreement between this model and the data.

Vers une approche globale de l'évolution des Hominidés

Abstract Two models of diversification of the common ancestor of gorillas, chimpanzees and men can be proposed on the basis of the distribution of chromosomal rearrangements in extant species and reconsideration of the role played by climate. The small genetic divergence between chimpanzees and humans is greatly amplified at the morphological level, thus constituting the ‘human paradox’. This paradox is resolved by the economical and flexible evolutionary mechanism of mutations in regulator genes and the heterochronies they control, which are the true internal clocks of evolution. Changes in cranial morphology are quantified and used to analyse and explain the steps in the transition from great ape to human morphology. By comparison at the various stages of development, it is suggested that from great apes to modern man numerous heterochronies have occured during ontogeny (hypermorphosis, hypomorphosis and post-displacements).

A solution to the human paradox : fundamental ontogenies and heterochronies

Solving the human paradox means explaining how a genetic difference of a mere 1% can be consistent with 5 million years of anatomical transformation from great apes to present-dayHomo sapiens. The solution proposed here is that of the internal history of ontogenetic change. A concept of “fundamental ontogeny” is developed and deduced from comparison between living and fossil primates. The fossil human lineage can be summarized into five fundamental ontogenies corresponding to successive skull plans (bauplans) resulting from five major phases of craniofacial contraction: prosimians (adapiforms), monkey apes (propliopithecidae), great apes (dryopithecidae), australopithecines andHomo. The morphological areas defined by these skull plans include more-or-less numerous species. This concept leads to renewed debate about (i) the relationship between speciation and bauplans, and (ii) the mechanisms involved in the successive steps of cranio-facial contraction and the correlated morphological changes. It is suggested that, from great apes to modern man, numerous heterochronies (hypermorphosis, hypomorphosis and post-displacements) have occurred during ontogeny, allowing the acquisition of permanent bipedalism inAustralopithecus andHomo, the increased cranial capacity of primitive forms ofHomo, and the disappearance of simian characters associated with renewed increase in cranial capacity inH. sapiens.