Arctic fox, Vulpes lagopus
Creationists have yet another inconvenient science paper to ignore, misrepresent, or distort. A new study led by Professor John Stewart of Bournemouth University, UK, and published in Trends in Ecology & Evolution, presents compelling evidence that environmental change—specifically the climatic fluctuations of the Ice Age—has been a major driver of evolution.
By examining both fossil and palaeogenetic data in the context of glaciation records, the research team has shown that adaptations to cold climates began emerging around 2.6 million years ago. This evolutionary process significantly accelerated about 700,000 years ago, when glacial cycles shifted and cold periods began lasting twice as long. During warmer interglacial phases, cold-adapted species appear to have retreated into climatic refugia, only to expand again as the ice returned.
The main, but not the only, cause of these periods of alternating glaciation and warmer climate were the Milankovitch cycles. For details, see the AI information panel.
Reindeer, Rangifer tarandus
Perhaps most damning to creationist dogma, the evolutionary events described took place hundreds of thousands—if not millions—of years before young-Earth creationists claim the planet was even formed. Depending on which apologetic is in play, creationists must now choose between proposing ludicrously accelerated post-Flood evolution or invoking the second law of thermodynamics in ways physicists and biologists would find baffling, using it to try to argue that events which can be observed could not have happened due to a fundamental law of physics.
What information do you have on Milakovich cycles? Milankovitch cycles are long-term variations in Earth’s orbit and orientation that affect the distribution and intensity of sunlight received on the planet’s surface. These astronomical cycles are named after the Serbian geophysicist Milutin Milankovitch, who, in the early 20th century, developed the theory that these variations influence Earth's climate patterns—especially the timing of glacial and interglacial periods during the Quaternary Ice Age.
Milankovitch cycles comprise three main components:
- Eccentricity (Orbital shape)
- Cycle length: \~100,000 years (with minor contributions at \~400,000 years).
- What it is: This refers to the shape of Earth's orbit around the Sun, which varies between more circular and more elliptical (oval).
- Effect: Affects the overall distance between Earth and the Sun and thus the total solar energy received, particularly influencing the difference in solar heating between perihelion (closest point) and aphelion (farthest point).
- Axial Tilt (Obliquity)
- Cycle length: \~41,000 years.
- What it is: Earth's axial tilt varies between about 22.1° and 24.5°. It’s currently about 23.5°.
- Effect: Changes the severity of the seasons—greater tilt means more extreme seasons (hotter summers and colder winters), while a smaller tilt leads to milder seasonal contrasts. This has a particularly strong influence on high-latitude ice sheet formation and melting.
- Precession (Axial Wobble)
- Cycle length: \~26,000 years.
- What it is: Earth's axis wobbles like a spinning top, causing the orientation of the axis (and hence the timing of the seasons) to shift gradually over time.
- Effect: Alters the timing of when seasons occur relative to Earth's position in its orbit. For example, Northern Hemisphere summers may occur near aphelion or perihelion depending on the phase of precession, influencing seasonal contrasts.
Combined Effect
These cycles interact to modulate the amount and distribution of solar radiation (insolation) received at different latitudes and seasons over tens to hundreds of thousands of years. It is this complex interplay that influences the advance and retreat of ice sheets, and hence the Pleistocene glacial-interglacial cycles.
For instance, colder summers in the Northern Hemisphere—due to a combination of high eccentricity, low axial tilt, and precession placing summer near aphelion—can prevent winter snow from melting, leading to gradual accumulation of ice and the onset of glaciation.
Scientific Importance
- Milankovitch’s theory was initially controversial, but it has been strongly supported by palaeoclimate data, especially from deep-sea sediment and ice cores.
- It explains the timing of glaciations but not their full magnitude, which is modulated by feedbacks such as albedo (reflectivity), greenhouse gas levels, and ocean circulation.
Study reveals different phases of evolution during ice age
A new study has provided fresh insights into how animals such as the woolly mammoth, musk ox and arctic fox evolved to survive the cold during the ice age.
A team of palaeontologists and palaeogeneticists studied ancient fossil and DNA evidence for the nature and timing of changes animals and plants in the Northern Hemisphere.
They have shown that cold-adapted animals started to evolve 2.6 million years ago when the permanent ice at the poles became more prevalent. There followed a time when the continental ice sheets expanded and contracted and around 700,000 years ago the cold periods doubled in length. This is when many of the current cold-adapted species, as well as extinct ones like mammoths, evolved.
The findings have been published in the journal Trend in Ecology and Evolution.
The cold-adapted species are amongst the most vulnerable animals and plants to ongoing climate change. Therefore, an understanding of how species evolved in the past is essential to help us understand the risks faced by endangered species today.
Professor John Stewart, lead author
Faculty of Science and Technology
Bournemouth University, Poole, Dorset, UK.
During their research, the team compared the evidence for evolution in plants and beetles with that for mammals and suggested that ideas that some organisms had evolved earlier in the polar regions need to be tested. This means that the way the modern Arctic ecologies assembled needs to be resolved as it is not clear when and how the animals and plants who live there came together.
The study found evidence for early occurrences of true lemmings and reindeer in the Arctic where they may have evolved as climates cooled in the early Pleistocene period, between one and two million years ago. The polar bear and arctic fox on the other hand may have joined them more recently within the last 700,000 years - colonising from the South. Some of the ice age cold species like the woolly rhino are different and may have evolved in the steppe grasslands to the south with the earliest occurrences in the Tibetan Plateau.
Publication:This is the first concerted effort to compare the evolution of cold-adapted animals and plants since modern methods of palaeogenetics appeared. We can now build on these findings to understand more about how more cold-adapted species evolved and how the Arctic ecologies arose in the past and use this to help conservation efforts in the future.
Professor John Stewart.
HighlightsThe findings from this study directly contradict key tenets of young-Earth creationism, which asserts that the Earth and all life on it were created in their current forms roughly 6,000 to 10,000 years ago. The evolutionary changes described—such as the gradual development of cold-adapted traits over the last 2.6 million years—occur on timescales that are orders of magnitude longer than creationist chronologies allow. These adaptations are shown to correlate with well-understood astronomical cycles, such as the 100,000-year eccentricity cycle, which simply do not fit into a young-Earth framework.
Cold-adapted vertebrate taxa underwent different phases of evolution during the last 3 million years. The first is the early appearance of some of the genera in the Pliocene to Early Pleistocene. There followed the appearance of many of the cold-adapted species after the time that glaciations more than doubled in length during the Middle Pleistocene. Since then there has also been climate-related species formation due to endemism through isolation, and when plant population range changes led to hybrid species.
Three different modes have been proposed for the evolution of cold-adapted taxa: the ‘out of the temperate zone’ hypothesis, the ‘evolving in situ’ hypothesis, and the ‘montane preadaptation’ hypothesis, all of which may have happened in different taxa at different times.
Palaeogenetic evidence has improved the precision of the timing of species origination as well as when and how species acquired their adaptations to the cold. The difference in the rates of evolution between vertebrates and other taxa (plants and beetles) may be overstated, and the absence of evidence may be masking similar evolutionary trends in rates and modes of evolution.
Abstract
The evolution of cold-adapted terrestrial species underwent two main phases. First, the genera of cold-adapted taxa appeared during the Late Pliocene to Early Pleistocene. The modern day and Late Pleistocene cold-adapted species then arose during and after the Middle Pleistocene Transition. These species evolved through one or more of the following processes: out of the temperate zone, evolving in situ, or through montane preadaptation. Palaeogenetic studies are greatly contributing to our understanding of the timings and modes of evolution of cold-adapted species as well as when their specialised traits evolved. The evolution of polar plant and beetle species is claimed to show greater stasis than that of vertebrates, but could instead reflect morphological conservatism that can be tested with palaeogenetics.
The cold as a novel environment
The cold-adapted plant and animal species found in polar and subpolar regions of the northern and southern hemispheres are amongst the species most vulnerable to ongoing climatic warming [1–3]. If we are to best understand the vulnerabilities of these cold-adapted organisms it is important to investigate their evolutionary origins and histories.
Cold-adapted terrestrial plant and animal taxa can be considered as organisms that expand their distributions during cold episodes such as the glacial (see Glossary) phases of Milankovitch cycles [4]. These taxa, by contrast, contract into refugia during warm interglacials [5]. However, because species are individualistic, the different cold-adapted taxa cannot be described as having identical adaptations, and some contract to higher latitudes and/or higher altitudes while others, the continental-adapted taxa, contract towards the centre of continents [4]. An alternative definition of cold-adapted taxa is based on their specific phenotypic traits. These include anatomical, physiological, and behavioural characteristics related to the cold itself, such as increased fat storage, increased thermal insulation, and more efficient oxygen transport, or other factors related to features of cold environments such as white hair or plumage [6]. Apart from the extinct taxa whose remains have been found in the permafrost [7], until recently it was usually only the living cold-adapted species whose phenotypic traits could be considered in terms of their relationship to the cold. However, with the advent of palaeogenetics, which uses ancient DNA (aDNA) to examine functional pathways encoded in animal and plant genomes, it has become possible to consider the evolution of cold adaptations through time in living and extinct taxa [8,9].
However, cold-adapted animal and plant species are a relatively recent phenomenon during the Cenozoic. This suggests that these taxa are likely to have evolved from more warm-adapted organisms. The likely timing of this evolution is in part limited by the timing of the initiation of permanent ice in the Arctic, which began in the late Miocene (ca. 10 million years ago, Ma) [10]. This process was reinforced during the Pleistocene when land ice became especially prevalent during the cold glacials of the Quaternary [11].
The terrestrial biomes that we associate today with cold climates are found towards the poles and at relatively high altitudes, namely the Tundra and the boreal Taiga forest. Some components of tundra are thought to have been present during the Pliocene [12], although the tundra biome was not yet in its present form [13]. During the Middle to Late Pleistocene glaciations, these cold biomes expanded from the poles and together with the dry continental grasslands (steppe) that expanded towards the oceanic areas they formed a largely extinct biome: the Steppe Tundra (mammoth steppe) of the Palaearctic and Nearctic [14].
Herein we review and compare the palaeontological and palaeogenetic evidence for how and when cold-adapted terrestrial taxa evolved. This review concentrates on northern hemisphere terrestrial vertebrates (mammals and one bird genus) that constitute modern boreal and tundra species as well as two Steppe Tundra species of the Pleistocene glaciations. Finally, we compare the vertebrate record with records of plants and beetles, which are thought to have different tempos and modes of evolution to cold adaptation.
Figure 1 Timeline for the evolution of cold-adapted vertebrate and plant taxa.
(A) The first occurrences of cold-adapted species and genera in the vertebrate fossil record. The first appearance range of the genus for seven species is older than 3.0 Ma (see also Table 1). (B) The availability of Early and Middle Pleistocene ancient DNA records (adapted with permission from [105], with data from [106,107]) that could be used to test the three hypotheses for the evolution of cold-adapted species. (C) Plant phylogenetic records document the maximum counts of arctic plant species arrival or in situ speciation events in 100 ka time bins (replotted from [80]). (D) Climatic cycles alternated between warm interglacials (IG, green shading) and cold glacials (G, blue shading) (adapted from [105] with LR04 oxygen isotope curve data from [108]). Purple shading denotes the timing of major climatic transitions associated with the evolution of cold adaptation. Animal silhouettes are from phylopic.org and represent taxa listed in the same order as Table 1 (from mammoth to rock ptarmigan) in panel A and deep-time mammalian palaeogenomes in panel B (see also [105] and references therein).
Moreover, the notion that species were specially created and remain unchanged since their origin is flatly contradicted by the fossil and genetic evidence presented. The researchers show that evolutionary pressures associated with repeated glacial cycles led to demonstrable changes in physiology, morphology, and even species distribution. These findings reinforce the Darwinian model of descent with modification in response to environmental change—an incremental, evidence-based process that has no place in creationist ideology, which relies on static kinds and sudden, miraculous appearances.
In addition, the study undermines creationist attempts to explain biodiversity through post-Flood rapid speciation. The idea that all extant species evolved from the limited number of animals allegedly saved on Noah’s Ark, within just a few thousand years, requires evolutionary rates that far exceed anything observed in nature. Ironically, this would imply hyper-evolution on a scale that makes mainstream evolutionary theory seem conservative by comparison. Yet, at the same time, many creationists invoke pseudoscientific misapplications of the second law of thermodynamics to argue that such evolutionary change is impossible.
Finally, the integration of palaeogenetics and palaeoclimatology in this study exemplifies the predictive and explanatory power of evolutionary science—something creationist models have consistently failed to deliver. No creationist theory predicted that species would track glacial cycles over millions of years, nor do they offer a coherent explanation for the observed patterns in the fossil and genetic records. This research not only fits seamlessly within the framework of evolutionary biology, but also highlights, once again, how creationist dogma is incompatible with the overwhelming body of scientific evidence.
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