Key points:
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Archived from the IMDb Discussion Forums — Everything Else
Lyman — 4 years ago(October 27, 2021 04:06 PM)
Key points:
Evidence for evolution comes from many different areas of biology:
Anatomy. Species may share similar physical features because the feature was present in a common ancestor (homologous structures).
Molecular biology. DNA and the genetic code reflect the shared ancestry of life. DNA comparisons can show how related species are.
Biogeography. The global distribution of organisms and the unique features of island species reflect evolution and geological change.
Fossils. Fossils document the existence of now-extinct past species that are related to present-day species.
Direct observation. We can directly observe small-scale evolution in organisms with short lifecycles (e.g., pesticide-resistant insects).
Introduction
Evolution is a key unifying principle in biology. As Theodosius Dobzhansky once said, “Nothing in biology makes sense except in the light of evolution.
But what, exactly, are the features of biology that make more sense through the lens of evolution? To put it another way, what are the indications or traces that show evolution has taken place in the past and is still happening today?
Evolution happens on large and small scales
Before we look at the evidence, let's make sure we are on the same page about what evolution is. Broadly speaking, evolution is a change in the genetic makeup (and often, the heritable features) of a population over time. Biologists sometimes define two types of evolution based on scale:
Macroevolution, which refers to large-scale changes that occur over extended time periods, such as the formation of new species and groups.
Microevolution, which refers to small-scale changes that affect just one or a few genes and happen in populations over shorter timescales.
Microevolution and macroevolution aren’t really two different processes. They’re the same process – evolution – occurring on different timescales. Microevolutionary processes occurring over thousands or millions of years can add up to large-scale changes that define new species or groups.
The evidence for evolution
In this article, we'll examine the evidence for evolution on both macro and micro scales.
First, we'll look at several types of evidence (including physical and molecular features, geographical information, and fossils) that provide evidence for, and can allow us to reconstruct, macroevolutionary events.
At the end of the article, we'll finish by seeing how microevolution can be directly observed, as in the emergence of pesticide-resistant insects.
Anatomy and embryology
Darwin thought of evolution as "descent with modification," a process in which species change and give rise to new species over many generations. He proposed that the evolutionary history of life forms a branching tree with many levels, in which all species can be traced back to an ancient common ancestor.
In this tree model, more closely related groups of species have more recent common ancestors, and each group will tend to share features that were present in its last common ancestor. We can use this idea to "work backwards" and figure out how organisms are related based on their shared features.
Homologous features
If two or more species share a unique physical feature, such as a complex bone structure or a body plan, they may all have inherited this feature from a common ancestor. Physical features shared due to evolutionary history (a common ancestor) are said to be homologous.
To give one classic example, the forelimbs of whales, humans, birds, and dogs look pretty different on the outside. That's because they're adapted to function in different environments. However, if you look at the bone structure of the forelimbs, you'll find that the pattern of bones is very similar across species. It's unlikely that such similar structures would have evolved independently in each species, and more likely that the basic layout of bones was already present in a common ancestor of whales, humans, dogs, and birds.
Some homologous structures can be seen only in embryos. For instance, all vertebrate embryos (including humans) have gill slits and a tail during early development. The developmental patterns of these species become more different later on (which is why your embryonic tail is now your tailbone, and your gill slits have turned into your jaw and inner ear). Homologous embryonic structures reflect that the developmental programs of vertebrates are variations on a similar plan that existed in their last common ancestor.
Sometimes, organisms have structures that are homologous to important structures in other organisms but that have lost their major ancestral function. These structures, which are often reduced in size, are known as vestigial structures. Examples of vestigial structures include the tailbone of humans (a vestigial tail), the hind leg bones of whales, and the underdeveloped legs found in some snakes.
Analogous features
To make things a little more interesting and complicated, not all physical features that look alike a -
Fun Guy From Yuggoth — 4 years ago(October 27, 2021 06:04 PM)
All that mystical mumbo-jumbo that you just posted above still doesn't explain how all that could have happened in mere 6000 years. And that is an indisputable proven fact since we are only able to observe stars and galaxies 6000 light years or closer at this point in time.
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Donna Acacia — 4 years ago(October 27, 2021 11:09 PM)
When I learned it, immediately I thought this theory of evolution explained all lifeforms on planet Earth except for human beings.
Even after biologists determined that chimpanzees share 98% of the same DNA sequences as humans. We still are greatly different. What compelled the chimpanzees to remain walking upright, lose most of its body hair, learn speech and built is home and all the other things homo sapiens are capable of doing? The had to be a motivation for survival. Chimpanzees and the other great apes survive fine like they are until we destroyed their habitat and even then the great apes are not evolving as quickly as mosquitos, virus, maggots and bacteria.
Why?
Now I'm thinking this:
Could be that all other animals evolved from homo sapiens? We, bacteria, viruses, maggots and those other species that evolve quickly are the first life forms on planet Earth? -
Fun Guy From Yuggoth — 4 years ago(October 27, 2021 11:25 PM)
From what I’ve gleaned over the years, the theory is about the walking upright part was that it was helpful in the tall grasslands to be able to see any approaching predators more easily, thus enabling them to survive and pass on their traits more frequently than the ones that didn’t go upright as well.
It would be just a guess, but I would imagine that it wasn’t all chimps everywhere that started evolving into more advanced hominids, but probably just a particular group of chimps that encountered some type of selective pressure due to their particular geographic location that other chimps weren’t exposed to that gave them an evolutionary advantage over ordinary chimps. Over the course of thousands or even millions of generations, these differences became more and more pronounced until I was finally born - the pinnacle of evolution thus far.
I am a super-monkey! -
Donna Acacia — 4 years ago(October 28, 2021 12:53 AM)
From what I’ve gleaned over the years, the theory is about the walking upright part was that it was helpful in the tall grasslands to be able to see any approaching predators more easily, thus enabling them to survive and pass on their traits more frequently than the ones that didn’t go upright as well.
Okay I am relying on information from Google in order to apply the science to the theory.
Who are predators in a grassland habitat?
Predators. Carnivorous predators inhabit grasslands in high numbers. Jaguars, Sumatran and Malayan tigers, lions, leopards, hyenas, cheetahs, African wild dogs, wolves and coyotes all patrol in search of grazing and roaming prey.
These are the species alive today. Early humans did have more hair on their bodies. That would make them blend in. But they also had the ability to craft crude weapons and other useful tools. The first humans probably interbreed when they migrated from Africa.
There's a video pdf
Dr. Rick Potts provides a video short introduction to some of the evidence for human evolution, in the form of fossils and artifacts
https://humanorigins.si.edu/education/introduction-human-evolution -
WarrenPeace — 4 years ago(October 28, 2021 02:11 AM)
WHEW!
You had me going for a minute there bud.
Getting all serious around here like that.
I was about to call the Straight Man Help Hotline on your behalf.
Their motto is, "We take a straight man and help him become gay for your pleasure!"
"Please vote to preserve the unique character of Warren…" - Robert Duvall -
MagneticMonopole — 4 years ago(October 28, 2021 12:36 AM)
What compelled the chimpanzees to remain walking upright, lose most of its body hair, learn speech and built is home and all the other things homo sapiens are capable of doing? The had to be a motivation for survival.
You fundamentally have no idea how evolution works. A species does not will, through motivation, changes to their DNA.
Could be that all other animals evolved from homo sapiens?
No. That's ignorant, batshit crazy lunacy.
The fossil and DNA records are very, very clear on what evolved from what. This is established science and there is no room for such ridiculous speculation. -
Donna Acacia — 4 years ago(October 28, 2021 12:54 AM)
It's not that I have no idea. It's that I have
forgotten
.
No. That's ignorant, batshit crazy lunacy.
The fossil and DNA records are very, very clear on what evolved from what. This is established science and there is no room for such ridiculous speculation.
Oh? My courses didn't focus on too much of that. So what evolved from what Mr. Brilliant?
Apes into hairless walking upright humans. Okay well then you're a white ape asshole. -
Donna Acacia — 4 years ago(October 28, 2021 01:12 AM)
And I'll show people that part you said about me being a tranny and teenage boy too. The routine is unfolding in my mind as I write this. I'll make them laugh at you. Dave Chappelle taught me how to talk to my audience while telling jokes.