Appearance Event Ordination
Encyclopedia
Appearance Event Ordination or AEO is a scientific method
for biochronology
through the ordering of the appearance of fossil
mammal
genera
by multivariate analysis
, using conjunctional (overlapping) and disconjunctional (nonoverlapping) range distributions in large sets of data.
into pairwise first-before-last statements. The wolf species Canis edwardii and Canis armbrusteri are used as example taxa for the following patterns. Each statement means that Canis edwardii, for example, must have first appeared before Canis armbusteri last appeared. This is true whenever either (1) Canis edwardii and Canis armbrusteri have been found together in at least one non-time averaged fossil collection, or (2) Canis edwardii is found lower in at least one lithostratigraphic
section than Canis armbrusteri.
algorithm
is applied to derive a first-pass hypothesized sequence of first and last appearances. The minimal constraint on this sequence is that if there is an observed, real-world Canis edwardii before Canis armbrusteri statement for any pair of taxa, the hypothesized event sequence must replicate it. Then the program shuffles the events using a maximum likelihood criterion. The criterion basically seeks to pull apart as many hypothesized age range overlaps as possible, especially if they involve common taxa. Taxa are defined as "common" if they are known to overlap with a large fraction of the taxa they are implied to overlap with.
algorithm that compares event sequence positions and geochronological
age estimates for collections that have them. The calibration only uses:
uses subjective opinions by published sources and/or authors citing authors such as Michael O. Woodburne, Robert W. Wilson, and J. David Archibald.
Appearance Event Ordination uses objective, explicit recordable, repeatable, and quantitative analyses
of faunal and biostratigraphic
data to arrive at a conclusion, according to John Alroy
.
Scientific method
Scientific method refers to a body of techniques for investigating phenomena, acquiring new knowledge, or correcting and integrating previous knowledge. To be termed scientific, a method of inquiry must be based on gathering empirical and measurable evidence subject to specific principles of...
for biochronology
Biochronology
Biochronology is the dating of biological events using biostratigraphic or palaeontological methods.-External links:* * *...
through the ordering of the appearance of fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
genera
Genera
Genera is a commercial operating system and development environment for Lisp machines developed by Symbolics. It is essentially a fork of an earlier operating system originating on the MIT AI Lab's Lisp machines which Symbolics had used in common with LMI and Texas Instruments...
by multivariate analysis
Multivariate analysis
Multivariate analysis is based on the statistical principle of multivariate statistics, which involves observation and analysis of more than one statistical variable at a time...
, using conjunctional (overlapping) and disconjunctional (nonoverlapping) range distributions in large sets of data.
Process
AEO is based on faunal overlap and stratigraphic superposition to derive a best-fit sequence of first and last appearance events.Step 1
The first step is to translate patterns of overlap and superpositionLaw of superposition
The law of superposition is a key axiom based on observations of natural history that is a foundational principle of sedimentary stratigraphy and so of other geology dependent natural sciences:...
into pairwise first-before-last statements. The wolf species Canis edwardii and Canis armbrusteri are used as example taxa for the following patterns. Each statement means that Canis edwardii, for example, must have first appeared before Canis armbusteri last appeared. This is true whenever either (1) Canis edwardii and Canis armbrusteri have been found together in at least one non-time averaged fossil collection, or (2) Canis edwardii is found lower in at least one lithostratigraphic
Lithostratigraphy
Lithostratigraphy is a sub-discipline of stratigraphy, the geological science associated with the study of strata or rock layers. Major focuses include geochronology, comparative geology, and petrology...
section than Canis armbrusteri.
Step 2
A multivariate ordinationOrdination
In general religious use, ordination is the process by which individuals are consecrated, that is, set apart as clergy to perform various religious rites and ceremonies. The process and ceremonies of ordination itself varies by religion and denomination. One who is in preparation for, or who is...
algorithm
Algorithm
In mathematics and computer science, an algorithm is an effective method expressed as a finite list of well-defined instructions for calculating a function. Algorithms are used for calculation, data processing, and automated reasoning...
is applied to derive a first-pass hypothesized sequence of first and last appearances. The minimal constraint on this sequence is that if there is an observed, real-world Canis edwardii before Canis armbrusteri statement for any pair of taxa, the hypothesized event sequence must replicate it. Then the program shuffles the events using a maximum likelihood criterion. The criterion basically seeks to pull apart as many hypothesized age range overlaps as possible, especially if they involve common taxa. Taxa are defined as "common" if they are known to overlap with a large fraction of the taxa they are implied to overlap with.
Step 3
Once the relative event sequence has been established, it is converted into numerical time with a non-linear interpolationInterpolation
In the mathematical field of numerical analysis, interpolation is a method of constructing new data points within the range of a discrete set of known data points....
algorithm that compares event sequence positions and geochronological
Geochronology
Geochronology is the science of determining the age of rocks, fossils, and sediments, within a certain degree of uncertainty inherent to the method used. A variety of dating methods are used by geologists to achieve this, and schemes of classification and terminology have been proposed...
age estimates for collections that have them. The calibration only uses:
- 40Argon/39Argon dates
- Uranium-thorium datesUranium-thorium datingUranium-thorium dating, also called thorium-230 dating, uranium-series disequilibrium dating or uranium-series dating, is a radiometric dating technique commonly used to determine the age of calcium carbonate materials such as speleothem or coral...
for some PleistocenePleistoceneThe Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....
collections - Paleomagnetic dates that derive from unambiguous, narrow correlations inferred using non-faunal tie points such as the position in the section of the K–T boundaryK–T boundaryThe K–T boundary is a geological signature, usually a thin band, dated to 65.5 ± 0.3 Ma ago. K is the traditional abbreviation for the Cretaceous period, and T is the abbreviation for the Tertiary period...
, Paleocene-Eocene boundary, or Recent.
NALMA vs. AEO
North American Land Mammal AgesNorth American Land Mammal Ages
The North American Mammal Ages establishes a geologic timescale for prehistoric North American fauna beginning 66.5 Ma during the Paleocene and continuing through to the Late Pleistocene...
uses subjective opinions by published sources and/or authors citing authors such as Michael O. Woodburne, Robert W. Wilson, and J. David Archibald.
Appearance Event Ordination uses objective, explicit recordable, repeatable, and quantitative analyses
Quantitative analysis
Quantitative analysis may refer to:* Quantitative analysis , an analysis technique applying mathematics stochastic calculus to finance...
of faunal and biostratigraphic
Biostratigraphy
Biostratigraphy is the branch of stratigraphy which focuses on correlating and assigning relative ages of rock strata by using the fossil assemblages contained within them. Usually the aim is correlation, demonstrating that a particular horizon in one geological section represents the same period...
data to arrive at a conclusion, according to John Alroy
John Alroy
John Alroy is a paleobiologist born in New York in 1966 and now residing in Sydney.-Area of expertise:Alroy specializes in diversity curves, speciation, and extinction of North American fossil mammals and Phanerozoic marine invertebrates, connecting regional and local diversity, taxonomic...
.