A human evolutionary tree. The dashed lines indicate that evolutionary relationships between species are uncertain. Note the 'bushiness' of the tree; the australopithecine line branches into several species of Australopithecus and also to several Homo species
The Modern Theory of Evolution is not just an interpretation of the fossil record. It's not even an interpretation of the fossil record, but an explanation of the genetic, cladistic, physiological, anatomical and molecular evidence, all of which converge on the same explanation, supported by, but not dependent on, the fossil record.
That conclusion is species have evolved from earlier ancestors by a process of evolutionary divergence from common ancestors.
The problem of being too dependent on the fossil record, which is inevitable when the genetic, physiological and biochemical evidence is no longer available is that, because of the rarity of fossilisation which depends on a body finding itself in the right place at the right time, is that it is essentially a random sampling process which produces a snapshot of the population at that time and place, randomly placed both temporally and geographically.
With some places (and times) being more conducive to producing fossils, this snapshot can easily be biased in favour of particular places and times appearing to be more important to the evolutionary process than they were in reality. There are fossil hotspots because those places favoured fossilisation, not because more of the species were concentrated there or because something about that place influenced the evolution of the species.
How and why can fossil hotspots give a distorted picture of evolution? Fossil hotspots, regions where an unusually high number of fossils are discovered, can indeed provide a skewed or distorted picture of evolution. Here's how and why this happens:To address this distortion caused by the inbuilt bias in the fossil record, two palaeobiologists from the Department of Anthropology and Center for the Advanced Study of Human Paleobiology at The George Washington University, Washington, USA, have used extant mammals, which were resident in the African Rift Valley alongside early hominins as analogues and shown how the fossil record obscures the picture of the distribution of these species, and so our picture of that of hominins.
- Sampling Bias
- Overrepresentation of Certain Species: Fossil hotspots can lead to an overrepresentation of species that lived in those specific regions. For example, if a hotspot contains a large number of fossils from a particular species, it might give the false impression that this species was more widespread or dominant in the past than it actually was.
- Geographical Bias: Since hotspots are often concentrated in certain areas (like the Burgess Shale in Canada or the Solnhofen Limestone in Germany), they might not reflect the true geographical distribution of species. This can lead to a skewed understanding of the range and distribution of ancient organisms.
- Temporal Bias
- Time-Specific Abundance: Some fossil hotspots may represent a very narrow time window in Earth's history. If a particular era or period is overrepresented in the fossil record, it might suggest that evolutionary changes or diversifications were happening more rapidly than they actually were.
- Environmental Bias
- Fossilization Conditions: The conditions that lead to fossilization are rare and often environment-specific. Areas where fossilization conditions were ideal (e.g., low oxygen environments that prevent decay) are more likely to become fossil hotspots. This can create a misleading picture where certain environments (like marine settings) seem to have more species diversity simply because those conditions were more likely to preserve fossils.
- Misleading Interpretation of Evolutionary Patterns
- Punctuated Equilibria Misinterpretation: The concept of punctuated equilibrium suggests that evolution happens in rapid bursts followed by long periods of stability. Fossil hotspots might artificially inflate the apparent speed of evolutionary changes if they happen to capture these "bursts" disproportionately.
- False Signals of Extinction Events: If a fossil hotspot abruptly ends, it might suggest an extinction event in the area, even though the species could have survived elsewhere. This can mislead scientists into thinking that certain species or groups were wiped out when they were not.
- Bias in Research Focus
- Uneven Research Effort: Fossil hotspots often attract more scientific attention and resources, leading to a more detailed understanding of those areas. This can result in an uneven picture where some parts of the fossil record are well understood, while others are poorly explored, leading to gaps in our understanding of evolution.
Conclusion
Fossil hotspots are invaluable for studying the history of life, but they can also distort our understanding of evolution if not carefully interpreted. Scientists must account for these biases by comparing data from multiple sites, considering the broader geological and environmental context, and using statistical methods to correct for sampling biases.
They have just published their findings in the journal Nature Ecology & Evolution and explained it in a George Washington University press release:
Fossil hotspots in Africa obscure a more complete picture of human evolution
New study shows how the mismatch between where fossils are preserved and where humans likely lived may influence our understanding of early human evolution.
Much of the early human fossil record originates from just a few places in Africa, where favorable geological conditions have preserved a trove of fossils used by scientists to reconstruct the story of human evolution. One of these fossil hotspots is the eastern branch of the East African Rift System, home to important fossil sites such as Olduvai Gorge in Tanzania. Yet, the eastern branch of the rift system only accounts for 1% of the surface area of Africa—a fact that makes it possible to estimate how much information scientists who rely on such small samples are missing.
In a new study published today in the journal Nature Ecology & Evolution, researchers at the George Washington University show the extent to which the concentration of sites in hotspots like the East African Rift System biases our understanding of human evolution and why scientists must take that bias into account when interpreting early human history.
Because the evidence of early human evolution comes from a small range of sites, it’s important to acknowledge that we don’t have a complete picture of what happened across the entire continent. If we can point to the ways in which the fossil record is systematically biased and not a perfect representation of everything, then we can adjust our interpretations by taking this into account.
Assistant Professor W. Andrew Barr, lead author
Department of Anthropology and Center for the Advanced Study of Human Paleobiology
The George Washington University, Washington DC, USA.
To determine the size of the bias in the fossil record, Barr and his co-author Bernard Wood, University Professor of Human Origins at GW, looked at the distribution of modern mammals that currently live in the rift valley. They found that very few medium- and large-bodied mammals are “rift specialists,” and the rift environment, in fact, represents on average 1.6 % of the total geographic range of modern mammal species.
In a second analysis, Barr and Wood looked at how the skulls of modern primates collected in the rift valley compared with the skulls of the same primates from other parts of the continent. They found that skulls from the rift valley represented less than 50% of the total variation among primate skulls in Africa.
While the science community has long recognized that the rift represents just a small sample of where ancient humans likely lived, the researchers say previous studies have not used modern mammals as analogs for human fossils to try to quantify the magnitude of the bias. Information from modern mammals can’t tell us exactly where else, and in what type of environments, our human ancestors lived, but they can provide clues that help us better understand the environments and physical differences of ancient humans, say the authors.
We must avoid falling into the trap of coming up with what looks like a comprehensive reconstruction of the human story, when we know we don’t have all of the relevant evidence. Imagine trying to capture the social and economic complexity of Washington D.C. if you only had access to information from one neighborhood. It helps if you can get a sense of how much information is missing.
Professor Bernard Wood, co-author
Department of Anthropology and Center for the Advanced Study of Human Paleobiology
The George Washington University, Washington DC, USA.
The researchers also note the need for the scientific community to look beyond the rift to identify new fossil sites and expand the geographic range of the fossil record.
There’s a smaller number of people who work outside these traditional hotspots and do the thankless labor of trying to find fossils in these contexts that are really hard to work in, where the geology isn’t favorable for finding fossils. It’s worth doing that sort of work to make our picture of mammal and human evolution from this time period more complete.
Assistant Professor W. Andrew Barr.
The paper, “Spatial sampling bias influences our understanding of early hominin evolution in eastern Africa,” was published August 20, 2024 in Nature Ecology & Evolution.
AbstractWhat emerges from this paper is how science, in contrast to creationism, strives to remove bias, either intentional or incidental, from the data, to ensure the conclusion is as well supported by the evidence as possible.
The eastern branch of the Eastern African Rift System (EARS) is the source of a large proportion of the early hominin fossil record, but it covers a tiny fraction (ca. 1%) of the continent. Here we investigate how this mismatch between where fossils are preserved and where hominins probably lived may influence our ability to understand early hominin evolution, using extant mammals as analogues. We show that the eastern branch of the EARS is not an environmentally representative sample of the full species range for nearly all extant rift-dwelling mammals. Likewise, when we investigate published morphometric datasets for extant cercopithecine primates, evidence from the eastern branch alone fails to capture major portions of continental-scale cercopithecine cranial morphospace. We suggest that extant rift-dwelling species should be used as analogues to place confidence intervals on hominin habitat reconstructions. Furthermore, given the north–south orientation of the eastern branch of the EARS, morphoclines that are not aligned along this major north–south axis are likely to be poorly sampled by sites in the eastern branch. There is a pressing need for research on the geography of early hominin morphoclines to estimate how morphologically representative the hominin fossil sample from the eastern branch may be.
Barr, W.A., Wood, B.
Spatial sampling bias influences our understanding of early hominin evolution in eastern Africa.
Nat Ecol Evol (2024). https://doi.org/10.1038/s41559-024-02522-5
© 2024 Springer Nature Ltd.
Reprinted under the terms of s60 of the Copyright, Designs and Patents Act 1988.
By contrast, creationism, as any perusal of a creationist deception site will show, is about ensuring as much bias as possible in included in the presentation of the 'facts', in order to comply with the oath the authors take that their conclusions will always agree with creationist dogma, and to supply the craving for confirmation bias in the creationist cult.
Creationists are often perplexed by the fact that science keeps on re-examining what we thought we knew, and frequently changes its collective mind, but what creationists find even more perplexing is the fact, that, despite regular reassurances by their cult leaders that it's been about to happen any day now, real soon, for the last 50 years or so, scientists never reassess the evidence and conclude that it was all done by magic because magic creation better explains the available evidence. The conclusion is invariably about how exactly the evidence aligns with the Theory of Evolution, about which there is no significant doubt in serious biology science circles, although there will always be debate about the precise details.
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