scholarly journals Ardipithecus hand provides evidence that humans and chimpanzees evolved from an ancestor with suspensory adaptations

2021 ◽  
Vol 7 (9) ◽  
pp. eabf2474
Author(s):  
Thomas C. Prang ◽  
Kristen Ramirez ◽  
Mark Grabowski ◽  
Scott A. Williams
Keyword(s):  
20Th Century ◽  
Common Ancestor ◽  
Comparative Methods ◽  
Early 20Th Century ◽  
Positional Behavior ◽  
Last Common Ancestor ◽  
Phylogenetic Comparative Methods ◽  
Anatomical Research ◽  
Vertical Climbing

The morphology and positional behavior of the last common ancestor of humans and chimpanzees are critical for understanding the evolution of bipedalism. Early 20th century anatomical research supported the view that humans evolved from a suspensory ancestor bearing some resemblance to apes. However, the hand of the 4.4-million-year-old hominin Ardipithecus ramidus purportedly provides evidence that the hominin hand was derived from a more generalized form. Here, we use morphometric and phylogenetic comparative methods to show that Ardipithecus retains suspensory adapted hand morphologies shared with chimpanzees and bonobos. We identify an evolutionary shift in hand morphology between Ardipithecus and Australopithecus that renews questions about the coevolution of hominin manipulative capabilities and obligate bipedalism initially proposed by Darwin. Overall, our results suggest that early hominins evolved from an ancestor with a varied positional repertoire including suspension and vertical climbing, directly affecting the viable range of hypotheses for the origin of our lineage.

scholarly journals Analysis of phenotypic evolution in Dictyostelia highlights developmental plasticity as a likely consequence of colonial multicellularity

2013 ◽  
Vol 280 (1764) ◽  
pp. 20130976 ◽  
Author(s):  
Maria Romeralo ◽  
Anna Skiba ◽  
Alejandro Gonzalez-Voyer ◽  
Christina Schilde ◽  
Hajara Lawal ◽  
...  
Keyword(s):  
Developmental Plasticity ◽  
Common Ancestor ◽  
Last Common Ancestor ◽  
Phylogenetic Comparative Methods ◽  
Control Mechanisms ◽  
Phenotypic Evolution ◽  
Phenotypic Characters ◽  
Large Structures ◽  
Group 4 ◽  
Local Cell

Colony formation was the first step towards evolution of multicellularity in many macroscopic organisms. Dictyostelid social amoebas have used this strategy for over 600 Myr to form fruiting structures of increasing complexity. To understand in which order multicellular complexity evolved, we measured 24 phenotypic characters over 99 dictyostelid species. Using phylogenetic comparative methods, we show that the last common ancestor (LCA) of Dictyostelia probably erected small fruiting structures directly from aggregates. It secreted cAMP to coordinate fruiting body morphogenesis, and another compound to mediate aggregation. This phenotype persisted up to the LCAs of three of the four major groups of Dictyostelia. The group 4 LCA co-opted cAMP for aggregation and evolved much larger fruiting structures. However, it lost encystation, the survival strategy of solitary amoebas that is retained by many species in groups 1–3. Large structures, phototropism and a migrating intermediate ‘slug’ stage coevolved as evolutionary novelties within most groups. Overall, dictyostelids show considerable plasticity in the size and shape of multicellular structures, both within and between species. This probably reflects constraints placed by colonial life on developmental control mechanisms, which, depending on local cell density, need to direct from 10 to a million cells into forming a functional fructification.

scholarly journals Multiple evolutionary origins and losses of tooth complexity in squamates

2020 ◽  
Author(s):  
Fabien Lafuma ◽  
Ian J. Corfe ◽  
Julien Clavel ◽  
Nicolas Di-Poï
Keyword(s):  
Late Jurassic ◽  
Evolutionary History ◽  
Common Ancestor ◽  
Critical Role ◽  
Comparative Methods ◽  
Vertebrate Evolution ◽  
Tooth Surface ◽  
Phylogenetic Comparative Methods ◽  
Evolutionary Origins ◽  
Complexity Increase

Teeth act as tools for acquiring and processing food and so hold a prominent role in vertebrate evolution1,2. In mammals, dental-dietary adaptations rely on tooth shape and complexity variations controlled by cusp number and pattern – the main features of the tooth surface3,4. Complexity increase through cusp addition has dominated the diversification of many mammal groups3,5-9. However, studies of Mammalia alone don’t allow identification of patterns of tooth complexity conserved throughout vertebrate evolution. Here, we use morphometric and phylogenetic comparative methods across fossil and extant squamates (“lizards” and snakes) to show they also repeatedly evolved increasingly complex teeth, but with more flexibility than mammals. Since the Late Jurassic, six major squamate groups independently evolved multiple-cusped teeth from a single-cusped common ancestor. Unlike mammals10,11, reversals to lower cusp numbers were frequent in squamates, with varied multiple-cusped morphologies in several groups resulting in heterogenous evolutionary rates. Squamate tooth complexity evolved in correlation with dietary change – increased plant consumption typically followed tooth complexity increases, and the major increases in speciation rate in squamate evolutionary history are associated with such changes. The evolution of complex teeth played a critical role in vertebrate evolution outside Mammalia, with squamates exemplifying a more labile system of dental- dietary evolution.

scholarly journals Multiple evolutionary origins and losses of tooth complexity in squamates

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Fabien Lafuma ◽  
Ian J. Corfe ◽  
Julien Clavel ◽  
Nicolas Di-Poï
Keyword(s):  
Late Jurassic ◽  
Common Ancestor ◽  
Critical Role ◽  
Comparative Methods ◽  
Vertebrate Evolution ◽  
Phylogenetic Comparative Methods ◽  
Pattern Complexity ◽  
Evolutionary Origins ◽  
Complexity Increase

AbstractTeeth act as tools for acquiring and processing food, thus holding a prominent role in vertebrate evolution. In mammals, dental-dietary adaptations rely on tooth complexity variations controlled by cusp number and pattern. Complexity increase through cusp addition has dominated the diversification of mammals. However, studies of Mammalia alone cannot reveal patterns of tooth complexity conserved throughout vertebrate evolution. Here, we use morphometric and phylogenetic comparative methods across fossil and extant squamates to show they also repeatedly evolved increasingly complex teeth, but with more flexibility than mammals. Since the Late Jurassic, multiple-cusped teeth evolved over 20 times independently from a single-cusped common ancestor. Squamates frequently lost cusps and evolved varied multiple-cusped morphologies at heterogeneous rates. Tooth complexity evolved in correlation with changes in plant consumption, resulting in several major increases in speciation. Complex teeth played a critical role in vertebrate evolution outside Mammalia, with squamates exemplifying a more labile system of dental-dietary evolution.

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