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Origin of the metazoan phyla: Molecular clocks confirm paleontological estimates
Open accessAbstract
The time of origin of the animal phyla is controversial. Abundant fossils from the major animal phyla are found in the Cambrian, starting 544 million years ago. Many paleontologists hold that these phyla originated in the late Neoproterozoic, during the 160 million years preceding the Cambrian fossil explosion. We have analyzed 18 protein-coding gene loci and estimated that protostomes (arthropods, annelids, and mollusks) diverged from deuterostomes (echinoderms and chordates) about 670 million years ago, and chordates from echinoderms about 600 million years ago. Both estimates are consistent with paleontological estimates. A published analysis of seven gene loci that concludes that the corresponding divergence times are 1,200 and 1,000 million years ago is shown to be flawed because it extrapolates from slow-evolving vertebrate rates to faster-evolving invertebrate rates, as well as in other ways.
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“Depending on the proteins, calibration points and rate substitution models used, these estimates range from 600 to 1200 Mya (Wray et al., 1996;Ayala et al., 1998;Bromham et al., 1998;Gu, 1998;Cutler, 2000).”
From The last common bilaterian ancestor (2002) · cites this paper as Ayala et al., 1998
In the citing paper
“Our data suggest that, inconsistent with most molecular clock estimates but consistent with paleontological predictions (e.g., refs. 13 and 14), bilaterians do not have a significant precambrian evolutionary history.”
From Estimating metazoan divergence times with a molecular clock (2004) · cites this paper as [13]
In the citing paper
“The combination of a rate constancy test with high resolution of long DNA sequences (two data sets totaling over 7,000 bp), use of a wide range of taxa and fossil dates (rather than reliance on a single calibration rate), and a maximum likelihood analysis makes this method more reliable than previous molecular dating techniques (11).”
From Testing the Cambrian explosion hypothesis by using a molecular dating technique (1998) · cites this paper as [23]
In the citing paper
“Molecular phylogenies based on sequence comparisons of protein domains shared by all bilaterians suggest that the time of divergence of these proteins may extend back to 600–1,200 million years (megaannuum; Ma) ago (11–16).”
From Precambrian animal diversity: Putative phosphatized embryos from the Doushantuo Formation of China (2000) · cites this paper as [12]
In the citing paper
“Among the limitations noted are nucleotide compositional bias, among site rate variation, and heterogeneous rates of evolution across lineages (12–16).”
From Evaluating hypotheses of basal animal phylogeny using complete sequences of large and small subunit rRNA (2001) · cites this paper as [15]
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Inferring the historical patterns of biological evolution
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“Estimates of absolute rates are often made by pairwise comparisons that necessarily average the rate differences on intervening branches (Easteal and Herbert 1997; Ayala, Rzhetsky, and Ayala 1998), thus underestimating the variability in rate.”
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Metadata
- Authors
- Ayala, F. J., Rzhetsky, A., & Ayala, F. J.
- Affiliations
- Institute of Molecular Evolutionary Genetics, Pennsylvania State University, University Park, PA 16802; Columbia Genome Center, Columbia University, New York, NY 10032; and Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697
- Pennsylvania State University (US)
- ORCID
- Rzhetsky, Andrey
- Venue
- Proceedings of the National Academy of Sciences
- Publisher
- National Academy of Sciences
- Published
- 1998-01-20
- Volume
- 95
- Issue
- 2
- Pages
- 606-611
- ISSN
- 0027-8424 (ISSN-L)
- 1091-6490
- PMC
- PMC18467
- OpenAlex
- W2146480768
- Cited by
- 342
- References
- 41
- Citations by year
- 2026: 1 · 2024: 7 · 2023: 6 · 2022: 2 · 2021: 3 · 2020: 1 · 2019: 4 · 2018: 1 · 2017: 5 · 2016: 7 · 2015: 5 · 2014: 8 · 2013: 13 · 2012: 7
- FWCI
- 41.96
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Locations
- Proceedings of the National Academy of Sciences (publishedVersion)
- Europe PMC (PubMed Central) (publishedVersion)
- PubMed Central (publishedVersion)
- PubMed (publishedVersion)
- eScholarship (California Digital Library) (submittedVersion, cc-by)
- Funders
- National Institutes of Health (5p01gm042397-05)
- National Institute of General Medical Sciences (GM 42397)
- Topics
- Physical Sciences › Earth and Planetary Sciences › Paleontology › Evolution and Paleontology Studies
- Life Sciences › Agricultural and Biological Sciences › Animal Science and Zoology › Marine Invertebrate Physiology and Ecology
- Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Genomics and Phylogenetic Studies
- Keywords
- divergence time estimation, Cambrian explosion, Neoproterozoic, protein-coding genes, molecular clock rates, invertebrate evolution, arthropods, Annelida, Mollusca, Echinodermata
- MeSH terms
- Animals, Fossils, Phylogeny, Proteins, Evolution, Molecular
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