10 how far back does the fossil record extend? Ideas

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Does the Cambrian Explosion Pose a Challenge to Evolution? – Common Question – BioLogos

The Cambrian Explosion does present a number of important questions, but it doesn’t challenge the fundamental correctness of the central thesis of evolution.

Artistic rendering of trilobites on seabottom during Cambrian Period

Artistic rendering of trilobites on sea-bottom during Cambrian Period

The Cambrian Explosion does present a number of important questions, but it doesn’t challenge the fundamental correctness of the central thesis of evolution.

The “Cambrian Explosion” refers to the appearance in the fossil record of most major animal body plans about 543 million years ago. The new fossils appear in an interval of 20 million years or less. On evolutionary time scales, 20 million years is a rapid burst that appears to be inconsistent with the gradual pace of evolutionary change. However, rapid changes like this appear at other times in the fossil record, often following times of major extinction. The Cambrian Explosion does present a number of interesting and important research questions. It does not, however, challenge the fundamental correctness of the central thesis of evolution.

The term “Cambrian Explosion” refers to the appearance and rapid diversification of most major living animal body plans (phyla) in the fossil record within an interval of perhaps 20 million years or less, a relatively short period in evolutionary history. This time is known as the Early Cambrian, and began around 543 million years ago. This time interval is recorded by some spectacular fossil deposits that include superbly preserved fossils of these early animals. Two famous examples are the Burgess Shale in Canada, and the Chengjiang in China.1 Despite the claims of some, the Cambrian was not the beginning of multicellular animal life; the latter has a fossil record that extends back at least 30 million years earlier.2

The Cambrian Explosion is often posed as a challenge for evolution because the sudden burst of change in the fossil record appears to be inconsistent with the more typical gradual pace of evolutionary change. However, although different in certain ways, there are other times of very rapid evolutionary change recorded in the fossil record—often following times of major extinction. The Cambrian Explosion does present a number of challenging and important questions because it represents the time during which the main branches of the animal tree of life became established. It does not create a challenge to the fundamental correctness of the central thesis of evolution, the descent of all living species from a common ancestor. This important period in the history of life extended over millions of years, plenty of time for the evolution of these new body plans (phyla) to occur. Furthermore, the fossil record provides numerous examples of organisms that appear transitional between living phyla and their common ancestors. The ongoing research about the Cambrian period is an exciting opportunity to advance our understanding of how evolutionary processes work, and the environmental factors shaping them.

The major animal body plans that appeared in the Cambrian Explosion did not include the appearance of modern animal groups such as: starfish, crabs, insects, fish, lizards, birds and mammals. These animal groups all appeared at various times much later in the fossil record.3 The forms that appeared in the Cambrian Explosion were more primitive than these later groups, and many of them were soft-bodied organisms. However, they did include the basic features that define the major branches of the tree of life to which later life forms belong. For example, vertebrates are part of the Chordata group. The chordates are characterized by a nerve cord, gill pouches and a support rod called the notochord. In the Cambrian fauna, we first see fossils of soft-bodied creatures with these characteristics. However, the living groups of vertebrates appeared much later. It is also important to realize that many of the Cambrian organisms, although likely near the base of major branches of the tree of life, did not possess all of the defining characteristics of modern animal body plans. These defining characteristics appeared progressively over a much longer period of time.4

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Cambrian Timeline

Interpretations of the “Cambrian Explosion”

Not all scientists accept the idea that the Cambrian Explosion represents an unusually rapid evolutionary transition. The fossil record is notoriously incomplete, particularly for small and soft-bodied forms. Some researchers argue that the apparent rapid diversification of body plans is an artifact of an increase in the rate of fossilization, due in part to the evolution of skeletons, which fossilize more effectively.5 Many of the early Cambrian animals possessed some type of hard mineralized structures (spines, spicules, plates, etc.). In many cases these, often very tiny, mineralized structures are all that are found as fossils. There were major changes in marine environments and chemistry from the late Precambrian into the Cambrian, and these also may have impacted the rise of mineralized skeletons among previously soft-bodied organisms.6

Most scientists are persuaded that something significant happened at the dawn of the Cambrian era and view the Cambrian Explosion as an area of exciting and productive research. For example, scientists are now gaining a better understanding of what existed before the Cambrian Explosion as a result of new fossil discoveries. Recent discoveries are filling in the fossil record for the Precambrian fauna with soft-bodied organisms like those in the Ediacaran Assemblages found around the world.7 Late Precambrian fossil discoveries also now include representatives of sponges, cnidarians (the group that includes modern jellyfish, corals and anemones), mollusks and various wormlike groups. Some of the new fossil discoveries, in fact, appear to be more primitive precursors of the later Cambrian body plans. The discovery of such precursors shows that the Cambrian organisms did not appear from thin air.8 Further discoveries will no doubt reveal more clearly the relationship of Precambrian organisms with the creatures found in the Burgess Shale and Chengjiang deposits.9

Genomic studies provide further insights into the origins of the Cambrian Explosion. Although the genetic divergence of organisms would have preceded the recognition of new body plans in the fossil record, accumulating genomic data is broadly consistent with the fossil record.10 Both point to the rise of the bilateria (bilaterally symmetric invertebrate animals) in the latest Precambrian Ediacaran, and their ecological explosion in diversity in the Cambrian.

Gastropod shell fossil dated back to the early Cambrian.

Unanswered questions

The sudden change of the Cambrian Era was, in relative terms, not too sudden for the process of evolution. The changes during the Cambrian Era did not occur over decades, centuries, or even thousands of years; they occurred over millions of years—plenty of time for evolutionary change. However, for millions of years beforehand, body plans of animals had remained relatively constant. Not until this time period did a significant change occur. The remaining questions are: What triggered the Cambrian Explosion? And why did so much change occur at this time? Several different theories address the origin of the Cambrian Explosion, proposing that dramatic environmental changes must have opened up new niches for natural selection to operate upon. These proposals include the runaway glaciation theory,11 which proposes that glaciers briefly covered much of the earth, and the resultant loss of habitat created bottlenecks where evolution could act more rapidly. Another theory suggests that a change in atmospheric oxygen led to this sudden burst in evolutionary changes.12 Yet another proposal is that major changes in the seafloor, from algae mat-covered surfaces in the late Precambrian to soft muddy bottoms later in the Cambrian, had dramatic evolutionary and ecological impacts.13

The Cambrian era fossils, providing answers

While the causes of the Cambrian Explosion remain a topic of open and exciting debate, the continued fossil discoveries from the Cambrian and Precambrian Eras are bringing more clarity to the evolutionary puzzle. These fossils provide valuable insight, particularly for envisioning the common ancestors of diverse groups. For instance, both vertebrates (fish) and echinoderms (sea urchins, starfish) are part of the group called deuterostomes. Without fossil evidence, it is hard to envision what a common ancestor would look like for these very different creatures. The Cambrian fossils are filling in the picture.14

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Last updated on August 02, 2022

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Does the Cambrian Explosion Pose a Challenge to Evolution?

Does the Cambrian Explosion Pose a Challenge to Evolution?

  • Author: biologos.org

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  • Sumary: The Cambrian Explosion does present a number of important questions, but it doesn’t challenge the fundamental correctness of the central thesis of evolution.

  • Matching Result: The “Cambrian Explosion” refers to the appearance in the fossil record of most major animal body plans about 543 million years ago.

  • Intro: Does the Cambrian Explosion Pose a Challenge to Evolution? – Common Question – BioLogosThe Cambrian Explosion does present a number of important questions, but it doesn’t challenge the fundamental correctness of the central thesis of evolution.Artistic rendering of trilobites on sea-bottom during Cambrian PeriodThe Cambrian Explosion does present a number…
  • Source: https://biologos.org/common-questions/does-the-cambrian-explosion-pose-a-challenge-to-evolution

When did eukaryotic cells (cells with nuclei and other internal …

When did eukaryotic cells (cells with nuclei and other internal ...

  • Author: scientificamerican.com

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  • Sumary: The origin of the eukaryotes–the kingdom of life that includes all of the higher plants and animals, including ourselves–took place in the heavily obscured early history of the earth. Consequently, there is still much speculation involved in answering this question. Carl Woese, a professor of microbiology at the…

  • Matching Result: “One of the less ambiguous sources of information is the fossil record. Work by Gonzalo Vidal of the University of Uppsala in Sweden indicates …

  • Intro: When did eukaryotic cells (cells with nuclei and other internal organelles) first evolve? What do we know about how they evolved from earlier life-forms?The origin of the eukaryotes–the kingdom of life that includes all of the higher plants and animals, including ourselves–took place in the heavily obscured early history of…
  • Source: https://www.scientificamerican.com/article/when-did-eukaryotic-cells/

The earliest fossil record of the animals and its significance

The earliest fossil record of the animals and its significance

  • Author: ncbi.nlm.nih.gov

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  • Sumary: The fossil record of the earliest animals has been enlivened in recent years by a series of spectacular discoveries, including embryos, from the Ediacaran to the Cambrian, but many issues, not least of dating and…

  • Matching Result: by GE Budd · 2008 · Cited by 149 — The claim would be that the oldest animal fossils of the Doushantuo Fm, dating back to just after the Nantuo glaciation (i.e. the Chinese glacial deposits …

  • Intro: The earliest fossil record of the animals and its significance Journal List Philos Trans R Soc Lond B Biol Sci v.363(1496); 2008 Apr 27 PMC2614223 Philos Trans R Soc Lond B Biol Sci. 2008 Apr 27; 363(1496): 1425–1434. AbstractThe fossil record of the earliest animals has been enlivened in recent…
  • Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2614223/

At the Origin of Animals: The Revolutionary Cambrian Fossil …

At the Origin of Animals: The Revolutionary Cambrian Fossil ...

  • Author: ncbi.nlm.nih.gov

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  • Sumary: The certain fossil record of animals begins around 540 million years ago, close to the base of the Cambrian Period. A series of extraordinary discoveries starting over 100 years ago with Walcott’s discovery…

  • Matching Result: by GE Budd · 2013 · Cited by 35 — The certain fossil record of animals begins around 540 million years ago, close to the base of the Cambrian Period. A series of extraordinary discoveries …

  • Intro: At the Origin of Animals: The Revolutionary Cambrian Fossil Record Journal List Curr Genomics v.14(6); 2013 Sep PMC3861885 Curr Genomics. 2013 Sep; 14(6): 344–354. AbstractThe certain fossil record of animals begins around 540 million years ago, close to the base of the Cambrian Period. A series of extraordinary discoveries starting…
  • Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3861885/

Using the Fossil Record to Evaluate Timetree Timescales

Using the Fossil Record to Evaluate Timetree Timescales

  • Author: frontiersin.org

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  • Sumary: The fossil and geologic records provide the primary data used to established absolute timescales for timetrees. For the paleontological evaluation of proposed timetree timescales, and for node-based methods for constructing timetrees, the…

  • Matching Result: by CR Marshall · 2019 · Cited by 34 — The 95% confidence interval on this part of the hominin fossil record using equation (8) extends to between 12.8 and 10.1 million years ago, …

  • Intro: Using the Fossil Record to Evaluate Timetree Timescales1. IntroductionDeveloping rigorous methods for using paleontological and geological data to estimate divergence times between lineages has proven challenging. Yet, these methods are needed for both the construction and evaluation of timetrees (Donoghue and Yang, 2016), trees where the relative branch lengths are…
  • Source: https://www.frontiersin.org/articles/10.3389/fgene.2019.01049/full

The Real Nature of the Fossil Record

The Real Nature of the Fossil Record

  • Author: icr.org

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  • Sumary: The fossil record leaves an inescapable impression on the honest observer. It certainly doesn’t communicate the macroevolutionary picture. The record of the past written in stone contains no evidence that any particular animal ever morphed into a fundamentally different type of animal. No trend can be found of gradual, Darwinian…

  • Matching Result: At least 95 percent of all animal fossils are of marine invertebrates. They are found in great variety, but all are well-designed for life in …

  • Intro: The Real Nature of the Fossil Record | The Institute for Creation Research The fossil record leaves an inescapable impression on the honest observer. It certainly doesn’t communicate the macroevolutionary picture. The record of the past written in stone contains no evidence that any particular animal ever morphed into a…
  • Source: https://www.icr.org/article/real-nature-fossil-record/

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Frequently Asked Questions About how far back does the fossil record extend?

If you have questions that need to be answered about the topic how far back does the fossil record extend?, then this section may help you solve it.

What is the age of our fossil record?

Paleontology is the study of fossils, including their age, method of formation, and evolutionary significance. Specimens are typically considered to be fossils if they are b>over 10,000 years old/b>, with the oldest fossils being between 3.48 billion years and 4.1 billion years old. The totality of fossils is known as the fossil record.

Is 3.5 million years old the oldest fossil known?

In actuality, 3.5 billion-year-old cyanobacteria from western Australian Archaean rocks are the oldest fossils that have been found.

Why does the fossil record have gaps in it?

Romer’s gap is named after paleontologist Alfred Romer, who first recognized it. Romer’s gap spanned from approximately 360 to 345 million years ago, corresponding to the first 15 million years of the Carboniferous Period.

What are the fossil record’s restrictions?

There are some drawbacks to using fossil records as proof of organic evolution, including: missing links (i.e., fossils that haven’t yet been found); destruction (earth movement/landslides mass movement may have destroyed existing fossils); and soft body parts that decompose without producing fossils.

Will there be a fossil shortage?

Oil can last up to 50 years, natural gas up to 53 years, and coal can last up to 114 years; it is predicted that we will run out of fossil fuels in this century; however, since renewable energy sources are not widely used, the rate at which we deplete our reserves could increase.

What fossil record is the oldest?

Microfossils found in a rock nearly 3.5 billion years old in Western Australia have been verified as the oldest fossils ever found and the earliest direct evidence of life on Earth by scientists at UCLA and the University of Wisconsin–Madison.

Which human fossil has been discovered to date?

Scientists determine the age of some of the oldest human bones The Omo One bones, discovered in Ethiopia, are among the oldest human remains ever discovered. Their exact age has been disputed for decades, but a new study claims they are roughly 233,000 years old.

What method is used to date fossils older than 60000 years?

These minerals can be dated using methods based on the radioactive decay of isotopes, which happens at known rates and is typically measured with lasers, mass spectrometers, and occasionally nuclear reactors.

Is the fossil record ever going to be finished?

The fossil record is incomplete for a variety of reasons, including the fact that many species lacked hard parts, which are much more likely to fossilize, some rocks and the fossils they contained have eroded and vanished, and the majority of organisms decomposed or were eaten by scavengers after they died.

Why is there such a gap in the fossil record?

Since most organisms quickly decompose after they die, dispersing their remains, and since fossilization requires the remains to be covered by sediments and remain undisturbed for thousands of years, it is thought that the fossil record is incomplete.

Is the fossil record trustworthy?

Only a small portion of the few organisms preserved as fossils have been recovered and studied by paleontologists, and in some cases, the succession of forms over time has been meticulously reconstructed.

Is there a dinosaur fossil that is entirely intact?

It is nearly impossible to estimate the precise number of uncollected fossils, including incomplete specimens and fragments like stray tail bones or teeth. Nevertheless, the number is unquestionably in the millions.

What has been discovered to be the most complete human fossil?

The fossil locality at Hadar where the pieces of Lucy’s skeleton were discovered is known to scientists as Afar Locality 288 (A.L. 288). Lucy, a 3.2 million-year-old fossil skeleton of a human ancestor, was discovered in 1974.

Why is a fossil record not entirely reliable?

When sedimentary rocks are deeply buried in the earth, the pressure from above and the temperature cause them to change into metamorphic rocks, which destroy fossils. As a result of this rock cycle, the fossil record has been lost.

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