"There is a grandeur in this view of life, with its several powers, having
been originally breathed into a few forms or into one; and that, whilst this
planet has gone cycling on according to the fixed law of gravity, endless
forms most beautiful and most wonderful have been, and are being, evolved,"
concludes Charles Darwin's seminal work "On the Origin of the Species."
Actually, the majority of species that have ever lived are now known to be
extinct by biologists.
Throughout Earth's history, the extinction of certain species has generally
been approximately balanced by the emergence of new ones, with a few
significant, brief imbalances known to scientists as mass extinction events.
It has long been accepted by scientists that large-scale extinctions trigger
"radiations," or fruitful times for species evolution—a concept known as
"creative destruction." Scientists at the Tokyo Institute of Technology's
Earth-Life Science Institute (ELSI) led a recent study that used machine
learning to look at the co-occurrence of fossil species. They discovered
that while radiations and extinctions are rarely related, mass extinctions
most likely don't cause radiations on a similar scale.
A fundamental idea in traditional theories of evolution is creative
destruction. It becomes evident that there are times when a large number of
species abruptly vanish and a large number of new species emerge.
Nonetheless, compared to extinction events, radiations of a similar size to
the mass extinctions—referred to as the mass radiations in this study—have
gotten significantly less attention. In this study, the effects of radiation
and extinction were compared during the so-called Phanerozoic Eon, the time
span for which fossils are accessible. Palaeontologists see significance in
the Phanerozoic, which is named from the Greek word for "apparent life" and
spans the most recent ~ 550 million years of Earth's ~4.5 billion-year
history: It is difficult to see the previous evolutionary record since the
majority of species that lived before this time were microorganisms that
were difficult to produce fossils. According to the new study, many of the
most remarkable periods of evolutionary radiation occurred when life entered
new evolutionary and ecological arenas, such as during the Cambrian
explosion of animal diversity and the Carboniferous expansion of forest
biomes. This suggests that creative destruction isn't a good description of
how species originated or went extinct during the Phanerozoic. It is unknown
if this is true over the previous ~ 3 billion years during which bacteria
dominated the environment because there is not much information on such
ancient diversity that has been documented to support a similar study.
A few of the worst mass extinction events in the Phanerozoic fossil record
have been recognized by paleontologists. These mostly include of the "Big
Five" mass extinctions, such the end-Permian mass extinction, which is
thought to have claimed the lives of over 70% of all species. Scientists
believe that human activities, particularly hunting and changes in land use
brought about by the growth of agriculture, is the primary cause of the
sixth mass extinction that may be upon us.
The extinction of the non-avian dinosaurs, known as the Cretaceous-Tertiary
extinction (sometimes shortened to "K-T," after the German spelling of the
term), is a well-known example of the preceding "Big Five" mass extinctions.
It is thought to have been triggered by a meteor strike that occurred around
65 million years ago. Based on the fossil record, scientists have concluded
that particularly fruitful radiations are produced after catastrophic
extinction events. For instance, it is commonly believed that in the K-T
dinosaur-erasing event, a wasteland was left behind, allowing creatures such
as mammals to recolonize and "radiate," leading to the evolution of numerous
new mammal species and, eventually, the emergence of humans. In other words,
maybe we wouldn't be here talking about this issue if the K-T event of
"creative destruction" hadn't happened.
In ELSI's "Agora," a spacious common area where scientists and guests
frequently have lunch and pick up new discussions, the new research began
with a casual talk. The authors of the paper, Jennifer Hoyal Cuthill, an
evolutionary biologist and research fellow at Essex University in the United
Kingdom, and Nicholas Guttenberg, a physicist and machine learning
specialist and current research scientist at Cross Labs collaborating with
GoodAI in the Czech Republic, were both post-doctoral scholars at ELSI when
the work started. They were discussing whether or not machine learning could
be used to visualize and comprehend the fossil record.
Before the COVID-19 pandemic started to limit international travel, they
visited ELSI and worked assiduously to expand their study to investigate the
relationship between radiation occurrences and extinction. By these talks,
they were able to connect their new findings to the range of theories
already in existence about radiation and catastrophic extinctions. They soon
discovered that the evolutionary patterns that machine learning had helped
them identify were fundamentally different from conventional
interpretations.
The researchers examined over 1 million records in a large, carefully
maintained public database that included almost 200,000 species, using a
unique application of machine learning to investigate the temporal
co-occurrence of species in the Phanerozoic fossil record.
"Some of the most challenging aspects of understanding the history of life
are the enormous timescales and numbers of species involved," stated Dr.
Hoyal Cuthill, the lead author. Through the visualization of this data in a
way that is legible by humans, new machine learning applications can be
beneficial. This implies that we may literally hold 500,000 years of
evolution in the palm of our hands and learn new things from what we
observe."
Using their objective methods, they discovered that 15 mass radiations, two
combined mass extinction-radiation events, and the "big five" mass
extinction events that had previously been identified by palaeontologists
were all included in the top 5% of significant disruptions in which
extinction outpaced radiation or vice versa. Interestingly, our
investigation discovered that the most similar mass radiations and
extinctions were extremely rarely paired in time, denying the concept of a
causal linkage between them. our is in contrast to earlier narratives that
emphasised the relevance of post-extinction radiations.
"The ecosystem is dynamic; you don't necessarily have to chip off an
existing piece to allow something new to appear," co-author Dr. Nicholas
Guttenberg remarked.
The group also discovered that radiations might, in fact, significantly
alter already-existing ecosystems—a concept the authors refer to as
"destructive creation." They discovered that, on average, 19 million years
after the Phanerozoic Eon, nearly every species that comprised an ecosystem
at that point had vanished. On the other hand, this turnover rate is
substantially larger during major extinctions or radiations.
This provides a fresh viewpoint on the processes driving the current sixth
extinction. Since the Quaternary epoch began 2.5 million years ago, there
have been numerous climatic changes, including abrupt shifts in the amount
of glacier cover in high-latitude areas of the planet. This indicates that
the already fragmented biodiversity is being further eroded by the current
sixth extinction, and the scientists predict it will take a minimum of 8
million years for the biodiversity to return to the long-term average of 19
million years. It is more difficult for the typical process of new species
origination to replace what is being lost when a species that may have lived
for millions of years is erased by an extinction that occurs under our
watch, according to Dr. Hoyal Cuthill.
