Chronospecies

Equilibrium models in population biology have demonstrated that accurate predictions of species diversity can be made without reference to particular taxa. We have extended the use of equilibrium models to examine patterns of phyletic diversification in the fossil record. We assume that (1) regions become saturated with respect to the number of taxa that can coexist; and (2) after that limit is reached, rates of speciation and extinction are very similar. Using these minimal constraints, and the standard precepts of evolutionary taxonomy (monophyly), we have generated evolutionary trees by stochastic simulation and classified their lineages into clades. Random processes with minimal constraints yield phyletic trees similar to those based upon the fossil record. Of particular interest are the patterns of clade origination and extinction and of intraclade diversity. For comparison with computer simulations, we present actual clades for the Reptilia. The similarities are striking, but some patterns of the fossil record are not simulated by random processes. For example, the late Cretaceous extinction may represent a fundamentally different type of evolutionary event. The simulation program and its comparison with the real world permits a clearer separation of stochastic and deterministic elements in the evolutionary record.

@article{doi101086627905,
    author = "Raup, David M. and Gould, Stephen Jay and Schöpf, Thomas J. M. and Simberloff, Daniel",
    title = "Stochastic Models of Phylogeny and the Evolution of Diversity",
    year = "1973",
    journal = "The Journal of Geology",
    abstract = "Equilibrium models in population biology have demonstrated that accurate predictions of species diversity can be made without reference to particular taxa. We have extended the use of equilibrium models to examine patterns of phyletic diversification in the fossil record. We assume that (1) regions become saturated with respect to the number of taxa that can coexist; and (2) after that limit is reached, rates of speciation and extinction are very similar. Using these minimal constraints, and the standard precepts of evolutionary taxonomy (monophyly), we have generated evolutionary trees by stochastic simulation and classified their lineages into clades. Random processes with minimal constraints yield phyletic trees similar to those based upon the fossil record. Of particular interest are the patterns of clade origination and extinction and of intraclade diversity. For comparison with computer simulations, we present actual clades for the Reptilia. The similarities are striking, but some patterns of the fossil record are not simulated by random processes. For example, the late Cretaceous extinction may represent a fundamentally different type of evolutionary event. The simulation program and its comparison with the real world permits a clearer separation of stochastic and deterministic elements in the evolutionary record.",
    url = "https://doi.org/10.1086/627905",
    doi = "10.1086/627905",
    openalex = "W2026989517",
    references = "doi101007978146158633315, doi101086627137, doi101111j174966321961tb35525x, doi101126science17740541065, doi1023072982232, openalexw1590525445, openalexw2145250129, openalexw2465044259, openalexw3135630760"
}

@incollection{doi101016s0920544608703236,
    title = "Chapter 3 Stochastic Models in Evolutionary Palaeontology",
    year = "1977",
    booktitle = "Developments in palaeontology and stratigraphy",
    url = "https://doi.org/10.1016/s0920-5446(08)70323-6",
    doi = "10.1016/s0920-5446(08)70323-6",
    openalex = "W1726680493"
}

Taxonomists working with late Cenozoic faunas tend to view living species as starting points for the evaluation of chronospecies (i.e., segments of evolutionary lineages subjectively designated as species) that extend backward in time from the Recent. This practice makes it possible to construct a survivorship curve for late Cenozoic chronospecies by evaluating all fossil lineages believed to have survived to the present day. A survivorship curve is produced by plotting the fraction of these lineages existing at any time that have not undergone enough phyletic evolution that their extant representatives are assigned to new species. This kind of surviviorship curve has been plotted for chronospecies of mammals using the beginning of the Würm, rather than the Recent, as an endpoint in order to avoid the effects of the Würm and post-Würm mass extinction. The survivorship curve reveals that all but a small fraction of established chronospecies have long durations relative to intervals of time during which distinctive higher taxa have arisen. Phyletic turnover of species has been remarkably slow. Most net evolutionary change must have been associated with saltational speciation. Even the large majority of genera must have arisen rapidly by one or more divergent speciation events. Estimates of rates of extinction suggest that the bottleneck effect, in which constriction of a lineage is followed by re-expansion as a distinct species, cannot be a major source of evolutionary change. These conclusions, based on the evaluation of mammalian phylogeny, seem also to apply to other taxa of animals, supporting the punctuational model of evolution. The long durations of hominid species imply that the evolution of humans, like that of other mammals, conforms to this model.

@article{doi101017s0094837300005662,
    author = "Stanley, Steven M.",
    title = "Chronospecies' longevities, the origin of genera, and the punctuational model of evolution",
    year = "1978",
    journal = "Paleobiology",
    abstract = "Taxonomists working with late Cenozoic faunas tend to view living species as starting points for the evaluation of chronospecies (i.e., segments of evolutionary lineages subjectively designated as species) that extend backward in time from the Recent. This practice makes it possible to construct a survivorship curve for late Cenozoic chronospecies by evaluating all fossil lineages believed to have survived to the present day. A survivorship curve is produced by plotting the fraction of these lineages existing at any time that have not undergone enough phyletic evolution that their extant representatives are assigned to new species. This kind of surviviorship curve has been plotted for chronospecies of mammals using the beginning of the Würm, rather than the Recent, as an endpoint in order to avoid the effects of the Würm and post-Würm mass extinction. The survivorship curve reveals that all but a small fraction of established chronospecies have long durations relative to intervals of time during which distinctive higher taxa have arisen. Phyletic turnover of species has been remarkably slow. Most net evolutionary change must have been associated with saltational speciation. Even the large majority of genera must have arisen rapidly by one or more divergent speciation events. Estimates of rates of extinction suggest that the bottleneck effect, in which constriction of a lineage is followed by re-expansion as a distinct species, cannot be a major source of evolutionary change. These conclusions, based on the evaluation of mammalian phylogeny, seem also to apply to other taxa of animals, supporting the punctuational model of evolution. The long durations of hominid species imply that the evolution of humans, like that of other mammals, conforms to this model.",
    url = "https://doi.org/10.1017/s0094837300005662",
    doi = "10.1017/s0094837300005662",
    openalex = "W2484245196",
    references = "doi10100703064746897, doi101017s0094837300005224, doi101093aesa383396, doi101126science1653891349, doi1023071441916, doi1023072407738, doi1023072411924, doi104159harvard9780674865327, openalexw2145250129, openalexw3135630760"
}

Taxonomists working with late Cenozoic faunas tend to view living species as starting points for the evaluation of chronospecies (i.e., segments of evolutionary lineages subjectively designated as species) that extend backward in time from the Recent. This practice makes it possible to construct a survivorship curve for late Cenozoic chronospecies by evaluating all fossil lineages believed to have survived to the present day. A survivorship curve is produced by plotting the fraction of these lineages existing at any time that have not undergone enough phyletic evolution that their extant representatives are assigned to new species. This kind of surviviorship curve has been plotted for chronospecies of mammals using the beginning of the Würm, rather than the Recent, as an endpoint in order to avoid the effects of the Würm and post-Würm mass extinction. The survivorship curve reveals that all but a small fraction of established chronospecies have long durations relative to intervals of time during which distinctive higher taxa have arisen. Phyletic turnover of species has been remarkably slow. Most net evolutionary change must have been associated with saltational speciation. Even the large majority of genera must have arisen rapidly by one or more divergent speciation events. Estimates of rates of extinction suggest that the bottleneck effect, in which constriction of a lineage is followed by re-expansion as a distinct species, cannot be a major source of evolutionary change. These conclusions, based on the evaluation of mammalian phylogeny, seem also to apply to other taxa of animals, supporting the punctuational model of evolution. The long durations of hominid species imply that the evolution of humans, like that of other mammals, conforms to this model.

@article{stanley1978chronospecies,
    author = "Stanley, Steven M.",
    title = "Chronospecies' longevities, the origin of genera, and the punctuational model of evolution",
    year = "1978",
    journal = "Paleobiology",
    abstract = "Taxonomists working with late Cenozoic faunas tend to view living species as starting points for the evaluation of chronospecies (i.e., segments of evolutionary lineages subjectively designated as species) that extend backward in time from the Recent. This practice makes it possible to construct a survivorship curve for late Cenozoic chronospecies by evaluating all fossil lineages believed to have survived to the present day. A survivorship curve is produced by plotting the fraction of these lineages existing at any time that have not undergone enough phyletic evolution that their extant representatives are assigned to new species. This kind of surviviorship curve has been plotted for chronospecies of mammals using the beginning of the Würm, rather than the Recent, as an endpoint in order to avoid the effects of the Würm and post-Würm mass extinction. The survivorship curve reveals that all but a small fraction of established chronospecies have long durations relative to intervals of time during which distinctive higher taxa have arisen. Phyletic turnover of species has been remarkably slow. Most net evolutionary change must have been associated with saltational speciation. Even the large majority of genera must have arisen rapidly by one or more divergent speciation events. Estimates of rates of extinction suggest that the bottleneck effect, in which constriction of a lineage is followed by re-expansion as a distinct species, cannot be a major source of evolutionary change. These conclusions, based on the evaluation of mammalian phylogeny, seem also to apply to other taxa of animals, supporting the punctuational model of evolution. The long durations of hominid species imply that the evolution of humans, like that of other mammals, conforms to this model.",
    url = "https://doi.org/10.1017/s0094837300005662",
    doi = "10.1017/s0094837300005662",
    number = "1",
    openalex = "W2484245196",
    pages = "26-40",
    volume = "4",
    references = "doi10100703064746897, doi101017s0094837300005224, doi101093aesa383396, doi101126science1653891349, doi1023071441916, doi1023072407738, doi1023072411924, doi104159harvard9780674865327, openalexw2145250129, openalexw3135630760"
}

@misc{stanley1978chronospecies1,
    author = "Stanley, S. M",
    title = "Chronospecies' longevities, the origin of genera, and the punctuational model of evolution",
    year = "1978",
    howpublished = "Paleobiology, v. 4, p. 26-40",
    note = "talkorigins\_source = {true}; raw\_reference = {Stanley, S. M., 1978, Chronospecies' longevities, the origin of genera, and the punctuational model of evolution: Paleobiology, v. 4, p. 26-40.}"
}

The effects of the application of horizontal (population) as opposed to vertical (typologic) taxonomy on precision of ammonite chronozonation are discussed and an example of stratigraphic inference that can be derived from the population method is presented. An almost complete macroconch from Świetoszewo, Pomerania, is compared with a standard, biometrically studied series of samples from the Early Volgian of Brzostowka, Central Poland. Specimens identical morphologically with that from Świetoszewo can be found among extreme end-members of the population variability much above and below the horizon of the best fit with the mean for the sample. Time correlation is thus a probabilistic kind of inference as the probable identity of time decreases with increasing distance from the horizon of the best fit. For this reason vertical (typologie) diagnoses of chronospecies cannot result in better and more rellable correlations than a horizontal (population) one. Because the typologie species concept leads to false representation in phylogenetics and biogeography it is proposed to abandon its use in biostratigraphy.

@article{openalexw821285779,
    author = "Dzik, Jerzy",
    title = "Typologic versus population concepts of chronospecies: implications for ammonite biostratigraphy",
    year = "1985",
    abstract = "The effects of the application of horizontal (population) as opposed to vertical (typologic) taxonomy on precision of ammonite chronozonation are discussed and an example of stratigraphic inference that can be derived from the population method is presented. An almost complete macroconch from Świetoszewo, Pomerania, is compared with a standard, biometrically studied series of samples from the Early Volgian of Brzostowka, Central Poland. Specimens identical morphologically with that from Świetoszewo can be found among extreme end-members of the population variability much above and below the horizon of the best fit with the mean for the sample. Time correlation is thus a probabilistic kind of inference as the probable identity of time decreases with increasing distance from the horizon of the best fit. For this reason vertical (typologie) diagnoses of chronospecies cannot result in better and more rellable correlations than a horizontal (population) one. Because the typologie species concept leads to false representation in phylogenetics and biogeography it is proposed to abandon its use in biostratigraphy.",
    url = "https://openalex.org/W821285779",
    openalex = "W821285779"
}

@article{doi101016037783988790020x,
    author = "Wei, Kuo‐Yen",
    title = "Multivariate morphometric differentiation of chronospecies in the late Neogene planktonic foraminiferal lineageGloboconella",
    year = "1987",
    journal = "Marine Micropaleontology",
    url = "https://doi.org/10.1016/0377-8398(87)90020-x",
    doi = "10.1016/0377-8398(87)90020-x",
    openalex = "W2043634432",
    references = "doi1010160025322771900533, doi101017s0094837300004000, doi101038369716c0, doi1023071377078, doi1023071485586, doi1023072288308, doi1023072412740, doi1023072528963, doi107312simp92414, openalexw1973558337"
}

@article{stanley1989the,
    author = "Stanley, Steven M",
    title = "The empirical case for the punctuational model of evolution",
    year = "1989",
    journal = "Journal of Social and Biological Structures",
    url = "https://doi.org/10.1016/0140-1750(89)90042-0",
    doi = "10.1016/0140-1750(89)90042-0",
    number = "2-3",
    openalex = "W2038851461",
    pages = "159-172",
    volume = "12",
    references = "doi101017s0094837300005224, doi101038325031a0, doi101086282975, doi101093genetics16297, doi101093genetics9441011, doi101111j155856461969tb03508x, doi1023072482053, doi104159harvard9780674865327, doi107312steb94536, openalexw2971318137"
}

A simple and robust model of biological evolution of an ecology of interacting species is introduced. The model self-organizes into a critical steady state with intermittent coevolutionary avalanches of all sizes; i.e., it exhibits ``punctuated equilibrium'' behavior. This collaborative evolution is much faster than non-cooperative scenarios since no large and coordinated, and hence prohibitively unlikely, mutations are involved.

@article{doi101103physrevlett714083,
    author = "Bak, Per and Sneppen, Kim",
    title = "Punctuated equilibrium and criticality in a simple model of evolution",
    year = "1993",
    journal = "Physical Review Letters",
    abstract = "A simple and robust model of biological evolution of an ecology of interacting species is introduced. The model self-organizes into a critical steady state with intermittent coevolutionary avalanches of all sizes; i.e., it exhibits ``punctuated equilibrium'' behavior. This collaborative evolution is much faster than non-cooperative scenarios since no large and coordinated, and hence prohibitively unlikely, mutations are involved.",
    url = "https://doi.org/10.1103/physrevlett.71.4083",
    doi = "10.1103/physrevlett.71.4083",
    openalex = "W1966151890",
    references = "doi1010160004698180901493, doi101016s0022519305800943, doi101017s0094837300005224, doi101038342780a0, doi101103physreva38364, doi101103physreva466724, doi101103physrevlett59381, doi101103physrevlett693539, doi101103physrevlett71101, doi1012019780429492594, pines2018emerging"
}

@incollection{clube1996evolution,
    author = "Clube, S. V. M.",
    title = "Evolution, Punctuational Crises and the Threat to Civilization",
    year = "1996",
    booktitle = "Worlds in Interaction: Small Bodies and Planets of the Solar System",
    url = "https://doi.org/10.1007/978-94-009-0209-1\_54",
    doi = "10.1007/978-94-009-0209-1\_54",
    openalex = "W2078463644",
    pages = "433-440",
    references = "doi1010079789401133784, doi101007bf00049549, doi101038363704a0, doi101038367033a0, doi101146annurevea11050183002333, doi101177095968369400400211, doi1023071782931, doi1023073901804, doi105860choice330281, openalexw1638717326"
}

@article{doi101046j13652540200100803x,
    author = "Charlesworth, Brian and Dempsey, N D",
    title = "A model of the evolution of the unusual sex chromosome system of Microtus oregoni",
    year = "2001",
    journal = "Heredity",
    url = "https://doi.org/10.1046/j.1365-2540.2001.00803.x",
    doi = "10.1046/j.1365-2540.2001.00803.x",
    openalex = "W2054790618",
    references = "doi10100797814615698629"
}

Cohorts of marine taxa that originated during recoveries from mass extinctions were commonly more widespread spatially than those originating at other times. Coupled with the recognition of a correlation between the geographic ranges and temporal longevities of marine taxa, this observation predicts that recovery taxa were unusually long-lived geologically. We analyzed this possibility by assessing the longevities of marine genus cohorts that originated in successive substages throughout the Phanerozoic. Results confirm that several mass extinction recovery cohorts were significantly longer lived than other cohorts, but this effect was limited to the post-Paleozoic, suggesting differences in the dynamics of Paleozoic versus post-Paleozoic diversification.

@article{miller2003increased,
    author = "Miller, Arnold I. and Foote, Michael",
    title = "Increased Longevities of Post-Paleozoic Marine Genera After Mass Extinctions",
    year = "2003",
    journal = "Science",
    abstract = "Cohorts of marine taxa that originated during recoveries from mass extinctions were commonly more widespread spatially than those originating at other times. Coupled with the recognition of a correlation between the geographic ranges and temporal longevities of marine taxa, this observation predicts that recovery taxa were unusually long-lived geologically. We analyzed this possibility by assessing the longevities of marine genus cohorts that originated in successive substages throughout the Phanerozoic. Results confirm that several mass extinction recovery cohorts were significantly longer lived than other cohorts, but this effect was limited to the post-Paleozoic, suggesting differences in the dynamics of Paleozoic versus post-Paleozoic diversification.",
    url = "https://doi.org/10.1126/science.1089719",
    doi = "10.1126/science.1089719",
    number = "5647",
    pages = "1030-1032",
    volume = "302"
}

@article{crossref2006gradual,
    title = "Gradual Versus Punctuational Evolution",
    year = "2006",
    journal = "Science",
    url = "https://doi.org/10.1126/science.314.5796.13g",
    doi = "10.1126/science.314.5796.13g",
    number = "5796",
    openalex = "W4210646514",
    pages = "13g-13g",
    volume = "314"
}

We tested the ability of six quantitative genetic models to explain the evolution of phenotypic means using an extensive database compiled by Gingerich. Our approach differs from past efforts in that we use explicit models of evolutionary process, with parameters estimated from contemporary populations, to analyze a large sample of divergence data on many different timescales. We show that one quantitative genetic model yields a good fit to data on phenotypic divergence across timescales ranging from a few generations to 10 million generations. The key feature of this model is a fitness optimum that moves within fixed limits. Conversely, a model of neutral evolution, models with a stationary optimum that undergoes Brownian or white noise motion, a model with a moving optimum, and a peak shift model all fail to account for the data on most or all timescales. We discuss our results within the framework of Simpson's concept of adaptive landscapes and zones. Our analysis suggests that the underlying process causing phenotypic stasis is adaptation to an optimum that moves within an adaptive zone with stable boundaries. We discuss the implication of our results for comparative studies and phylogeny inference based on phenotypic characters.

@article{doi101086510633,
    author = "Estes, Suzanne and Arnold, Stevan J.",
    title = "Resolving the Paradox of Stasis: Models with Stabilizing Selection Explain Evolutionary Divergence on All Timescales",
    year = "2007",
    journal = "The American Naturalist",
    abstract = "We tested the ability of six quantitative genetic models to explain the evolution of phenotypic means using an extensive database compiled by Gingerich. Our approach differs from past efforts in that we use explicit models of evolutionary process, with parameters estimated from contemporary populations, to analyze a large sample of divergence data on many different timescales. We show that one quantitative genetic model yields a good fit to data on phenotypic divergence across timescales ranging from a few generations to 10 million generations. The key feature of this model is a fitness optimum that moves within fixed limits. Conversely, a model of neutral evolution, models with a stationary optimum that undergoes Brownian or white noise motion, a model with a moving optimum, and a peak shift model all fail to account for the data on most or all timescales. We discuss our results within the framework of Simpson's concept of adaptive landscapes and zones. Our analysis suggests that the underlying process causing phenotypic stasis is adaptation to an optimum that moves within an adaptive zone with stable boundaries. We discuss the implication of our results for comparative studies and phylogeny inference based on phenotypic characters.",
    url = "https://doi.org/10.1086/510633",
    doi = "10.1086/510633",
    openalex = "W2120631206",
    references = "doi10100797894010058529, doi101023a1013311015886, doi101038scientificamerican117998, doi101046j14390388200200356x, doi101086284325, doi101086383584, doi101111j155856461983tb00236x, doi1023072485224, doi102307jctvjsf433, doi105860choice396411, openalexw1591710988, openalexw3135630760"
}

@article{doi101016jjas200711018,
    author = "Escudé, Élise and Montuire, Sophie and Desclaux, Emmanuel and Quéré, Jean‐Pierre and Renvoisé, Élodie and Jeannet, Marcel",
    title = "Reappraisal of ‘chronospecies’ and the use of Arvicola (Rodentia, Mammalia) for biochronology",
    year = "2008",
    journal = "Journal of Archaeological Science",
    url = "https://doi.org/10.1016/j.jas.2007.11.018",
    doi = "10.1016/j.jas.2007.11.018",
    openalex = "W2006009839",
    references = "doi10100797814615698629, doi101016001046559290019u, doi1010160146664x8290034x, doi101016016953479390024j, doi101017cbo9780511529870, doi101017s0003598x00047001, doi101201978100307787915, doi1023071223169, openalexw601860967, openalexw623186629"
}

The study of mammalian evolution is often based on insights into the evolution of teeth. Developmental studies may attempt to address the mechanisms that guide evolutionary changes. One example is the new developmental model proposed by Kavanagh et al. (2007), which provides a high-level testable model to predict mammalian tooth evolution. It is constructed on an inhibitory cascade model based on a dynamic balance of activators and inhibitors, regulating differences in molar size along the lower dental row. Nevertheless, molar sizes in some mammals differ from this inhibitory cascade model, in particular in voles. The aim of this study is to point out arvicoline and murine differences within this model and to suggest an alternative model. Here we demonstrate that the inhibitory cascade is not followed, due to the arvicoline's greatly elongated first lower molar. We broaden the scope of the macroevolutionary model by projecting a time scale onto the developmental model. We demonstrate that arvicoline evolution is rather characterized by a large gap from the oldest vole to more recent genera, with the rapid acquisition of a large first lower molar contemporaneous to their radiation. Our study provides alternative evolutionary hypotheses for mammals with different trajectories of development.

@article{doi101111j15585646200900639x,
    author = "Renvoisé, Élodie and Evans, Alistair R. and Jebrane, Ahmad and Labruère, Catherine and Laffont, Rémi and Montuire, Sophie",
    title = "EVOLUTION OF MAMMAL TOOTH PATTERNS: NEW INSIGHTS FROM A DEVELOPMENTAL PREDICTION MODEL",
    year = "2009",
    journal = "Evolution",
    abstract = "The study of mammalian evolution is often based on insights into the evolution of teeth. Developmental studies may attempt to address the mechanisms that guide evolutionary changes. One example is the new developmental model proposed by Kavanagh et al. (2007), which provides a high-level testable model to predict mammalian tooth evolution. It is constructed on an inhibitory cascade model based on a dynamic balance of activators and inhibitors, regulating differences in molar size along the lower dental row. Nevertheless, molar sizes in some mammals differ from this inhibitory cascade model, in particular in voles. The aim of this study is to point out arvicoline and murine differences within this model and to suggest an alternative model. Here we demonstrate that the inhibitory cascade is not followed, due to the arvicoline's greatly elongated first lower molar. We broaden the scope of the macroevolutionary model by projecting a time scale onto the developmental model. We demonstrate that arvicoline evolution is rather characterized by a large gap from the oldest vole to more recent genera, with the rapid acquisition of a large first lower molar contemporaneous to their radiation. Our study provides alternative evolutionary hypotheses for mammals with different trajectories of development.",
    url = "https://doi.org/10.1111/j.1558-5646.2009.00639.x",
    doi = "10.1111/j.1558-5646.2009.00639.x",
    openalex = "W2014222673",
    references = "doi10100797814615698629"
}

@article{holliday2009genes,
    author = "Holliday, Robin",
    title = "Genes and the evolution of longevities",
    year = "2009",
    journal = "Biogerontology",
    url = "https://doi.org/10.1007/s10522-008-9153-7",
    doi = "10.1007/s10522-008-9153-7",
    number = "1",
    pages = "1-2",
    volume = "10"
}

Fifty years ago, the hominin species Homo habilis was described by Leakey, Tobias and Napier (1964) on the basis of cranial and postcranial remains from Bed I at Ol duvai Gorge in Tanzania, dated at about 1.8 million years ago (mya). The reaction was highly critical. Sceptics included W.E. Le Gros Clark, K. Oakley, B.G. Campbell, D. Pilbeam, E.L. Simons, F.C. Howell, J. Robinson and L. Brace (Tobias, 1992). Some noted that the new material was similar to South African Plio-Pleistocene fossils attributed to Australopithecus africanus from sites such as Taung (described initially by Dart, 1925) and Sterkfontein (described by Broom and Robinson since 1936, see Broom et al., 1950). Critics claimed that a new species (habilis) in the genus Homo was unwarranted. Robinson (1965) argued that the specimens attributed to H. habilis should instead be considered to be australopithecines. It was not until some 25 years later that Tobias (1991) published two detailed volumes on the hominin fossils attributed to H. habilis from Olduvai Gorge. By that time these specimens were generally considered as a valid species. Tobias (1992) himself triumphantly wrote a retrospective assessment of the controversy, concluding with the words “Today it is widelyaccepted as a good taxon and one that represents a critical stage in the evolution of modern man”. However, there is reason to re-assess the status of certain specimens attributed to Homo habilis and A. africanus.

@incollection{doi101201b194107,
    author = "Thackeray, Francis",
    title = "HOMO HABILIS AND AUSTRALOPITHECUS AFRICANUS, IN THE CONTEXT OF A CHRONOSPECIES AND CLIMATIC CHANGE",
    year = "2015",
    abstract = "Fifty years ago, the hominin species Homo habilis was described by Leakey, Tobias and Napier (1964) on the basis of cranial and postcranial remains from Bed I at Ol duvai Gorge in Tanzania, dated at about 1.8 million years ago (mya). The reaction was highly critical. Sceptics included W.E. Le Gros Clark, K. Oakley, B.G. Campbell, D. Pilbeam, E.L. Simons, F.C. Howell, J. Robinson and L. Brace (Tobias, 1992). Some noted that the new material was similar to South African Plio-Pleistocene fossils attributed to Australopithecus africanus from sites such as Taung (described initially by Dart, 1925) and Sterkfontein (described by Broom and Robinson since 1936, see Broom et al., 1950). Critics claimed that a new species (habilis) in the genus Homo was unwarranted. Robinson (1965) argued that the specimens attributed to H. habilis should instead be considered to be australopithecines. It was not until some 25 years later that Tobias (1991) published two detailed volumes on the hominin fossils attributed to H. habilis from Olduvai Gorge. By that time these specimens were generally considered as a valid species. Tobias (1992) himself triumphantly wrote a retrospective assessment of the controversy, concluding with the words “Today it is widelyaccepted as a good taxon and one that represents a critical stage in the evolution of modern man”. However, there is reason to re-assess the status of certain specimens attributed to Homo habilis and A. africanus.",
    url = "https://doi.org/10.1201/b19410-7",
    doi = "10.1201/b19410-7",
    openalex = "W3176035964",
    references = "doi101006jhev19951008"
}

Abstract Here we explore variation and similarities in the two best-represented population groups who lived during the Middle Stone Age and Middle Palaeolithic—the Neanderthals and Homo sapiens. Building on approaches such as gene-culture co-evolution, we propose a four-field model to discuss relationships between human cognitive evolution, biology, technology, society, and ecology. We focus on the pre-50-ka phase, because we reason that later admixing between Neanderthals and Homo sapiens in Eurasia may make it difficult to separate them in terms of cognition, or any of the other fields discussed in this paper. Using our model enabled us to highlight similarities in cognition between the two populations in terms of symbolic behaviour and social learning and to identify differences in aspects of technical and social cognition. Dissimilarities in brain-selective gene variants and brain morphology strongly suggest differences in some evolutionary trajectories that would have affected cognition. We therefore suggest that rather than insisting that Neanderthals were cognitively ‘the same’ as Homo sapiens, it may be useful to focus future studies on Neanderthal-specific cognition that may have been well-developed within their specific context at the time.

@article{doi101007s10816020095026,
    author = "Lombard, Marlize and Högberg, Anders",
    title = "Four-Field Co-evolutionary Model for Human Cognition: Variation in the Middle Stone Age/Middle Palaeolithic",
    year = "2021",
    journal = "Journal of Archaeological Method and Theory",
    abstract = "Abstract Here we explore variation and similarities in the two best-represented population groups who lived during the Middle Stone Age and Middle Palaeolithic—the Neanderthals and Homo sapiens. Building on approaches such as gene-culture co-evolution, we propose a four-field model to discuss relationships between human cognitive evolution, biology, technology, society, and ecology. We focus on the pre-50-ka phase, because we reason that later admixing between Neanderthals and Homo sapiens in Eurasia may make it difficult to separate them in terms of cognition, or any of the other fields discussed in this paper. Using our model enabled us to highlight similarities in cognition between the two populations in terms of symbolic behaviour and social learning and to identify differences in aspects of technical and social cognition. Dissimilarities in brain-selective gene variants and brain morphology strongly suggest differences in some evolutionary trajectories that would have affected cognition. We therefore suggest that rather than insisting that Neanderthals were cognitively ‘the same’ as Homo sapiens, it may be useful to focus future studies on Neanderthal-specific cognition that may have been well-developed within their specific context at the time.",
    url = "https://doi.org/10.1007/s10816-020-09502-6",
    doi = "10.1007/s10816-020-09502-6",
    openalex = "W3119462367",
    references = "doi101016jquaint201802036"
}

@incollection{crossref2023punctuational,
    title = "punctuational, adj.",
    year = "2023",
    booktitle = "Oxford English Dictionary",
    url = "https://doi.org/10.1093/oed/1194385627",
    doi = "10.1093/oed/1194385627"
}

The evolution of metastasis, the spread of cancer to distal sites within the body, represents a lethal stage of cancer progression. Yet, the evolutionary dynamics that shape the emergence of metastatic disease remain unresolved. Here, using single-cell lineage tracing data in combination with phylogenetic statistical methods, we show that the evolutionary trajectory of metastatic disease is littered with bursts of rapid molecular change as new cellular subpopulations appear, a pattern known as punctuational evolution. Next, by measuring punctuational evolution across the metastatic cascade, we show that punctuational effects are concentrated within the formation of secondary tumours at distal metastatic sites, suggesting that qualitatively different modes of evolution may drive primary and metastatic tumour progression. Taken as a whole, our findings provide empirical evidence for distinct patterns of molecular evolution at early and late stages of metastatic disease and our approach provides a framework to study the evolution of metastasis at a more nuanced level than has been previously possible.

@article{butler2025punctuational,
    author = "Butler, George and Amend, Sarah R. and Venditti, Chris and Pienta, Kenneth J.",
    title = "Punctuational evolution is pervasive in distal site metastatic colonization",
    year = "2025",
    journal = "Proceedings of the Royal Society B: Biological Sciences",
    abstract = "The evolution of metastasis, the spread of cancer to distal sites within the body, represents a lethal stage of cancer progression. Yet, the evolutionary dynamics that shape the emergence of metastatic disease remain unresolved. Here, using single-cell lineage tracing data in combination with phylogenetic statistical methods, we show that the evolutionary trajectory of metastatic disease is littered with bursts of rapid molecular change as new cellular subpopulations appear, a pattern known as punctuational evolution. Next, by measuring punctuational evolution across the metastatic cascade, we show that punctuational effects are concentrated within the formation of secondary tumours at distal metastatic sites, suggesting that qualitatively different modes of evolution may drive primary and metastatic tumour progression. Taken as a whole, our findings provide empirical evidence for distinct patterns of molecular evolution at early and late stages of metastatic disease and our approach provides a framework to study the evolution of metastasis at a more nuanced level than has been previously possible.",
    url = "https://doi.org/10.1098/rspb.2024.2850",
    doi = "10.1098/rspb.2024.2850",
    number = "2039",
    openalex = "W4406640873",
    volume = "292",
    references = "doi101007bf00160154, doi101016jcell201303021, doi101016jcell201611037, doi101017s0094837300005224, doi10103844766, doi101038nature10762, doi101038nature14347, doi101056nejmoa1616288, doi10108010635150490522232, openalexw3135630760"
}

I have devised two tests that pit punctuationalism against gradualism. The first is the Test of Adaptive Radiation, which I apply to families of middle Eocene Mammalia and Late Cretaceous Bivalvia. This test shows that species in both of these classes lasted much too long for evolution within them (phyletic evolution) to have produced the new families that arose during brief time intervals. This test would yield similar results for many other taxa. It supports the punctuational model, as does the Test of Living Fossils, which predicts that long, slender clades, having experienced little speciation, should have undergone little evolution. Limited largely to phyletic evolution, this is exactly what happened to them. Several multivariate morphological studies of numerous fossil lineages have found little or no gradual evolution to have been the norm. One of these included 153 lineage traits and another, 250. Still another produced a rectangular stratophenetic phylogeny, with inferred horizontal speciation events connecting vertical lineages. Taken together these studies provide overwhelming support for the punctuational model. Many studies have shown that rapid speciation events occur frequently and some are punctuational. Jellyfishes that have appeared recently in saltwater lakes on the Pacific island of Palau are remarkable examples of punctuational speciation, and so is the sudden appearance of the novel sand dollar family Dendrasteridae in the California Miocene. The punctuational model shows that the value of sexual reproduction must be in producing long-lived adaptive radiations, whereas clones die out quickly.

@article{stanley2025why,
    author = "Stanley, Steven M.",
    title = "Why the punctuational model of evolution is valid",
    year = "2025",
    journal = "Paleobiology",
    abstract = "I have devised two tests that pit punctuationalism against gradualism. The first is the Test of Adaptive Radiation, which I apply to families of middle Eocene Mammalia and Late Cretaceous Bivalvia. This test shows that species in both of these classes lasted much too long for evolution within them (phyletic evolution) to have produced the new families that arose during brief time intervals. This test would yield similar results for many other taxa. It supports the punctuational model, as does the Test of Living Fossils, which predicts that long, slender clades, having experienced little speciation, should have undergone little evolution. Limited largely to phyletic evolution, this is exactly what happened to them. Several multivariate morphological studies of numerous fossil lineages have found little or no gradual evolution to have been the norm. One of these included 153 lineage traits and another, 250. Still another produced a rectangular stratophenetic phylogeny, with inferred horizontal speciation events connecting vertical lineages. Taken together these studies provide overwhelming support for the punctuational model. Many studies have shown that rapid speciation events occur frequently and some are punctuational. Jellyfishes that have appeared recently in saltwater lakes on the Pacific island of Palau are remarkable examples of punctuational speciation, and so is the sudden appearance of the novel sand dollar family Dendrasteridae in the California Miocene. The punctuational model shows that the value of sexual reproduction must be in producing long-lived adaptive radiations, whereas clones die out quickly.",
    url = "https://doi.org/10.1017/pab.2025.10058",
    doi = "10.1017/pab.2025.10058",
    number = "4",
    openalex = "W4416981381",
    pages = "631-644",
    volume = "51",
    references = "doi101007s100219900037, doi101073pnas0704088104, doi101073pnas722646, doi101111j001438202004tb01740x, doi101111j155856461971tb01868x, doi101126science28854691211, doi101579004474472912, doi101890024045, doi107312simp93764, doi107312steb94536"
}