How do new clades evolve?

[Guest Apostate Abe]

Hello! 

I have a quick question. Aronra states in his videos that we don't grow out of our ancestry and we will always be what our ancestors were. My question is how exactly do new clades evolve and what would be the criteria scientists use to determine if something has started a new clade? 

Thanks. 

Apostate Abe
Recovering YEC fundie  

[brachiosteve 14]

Hi Abe.

Those are good questions. We had a live book club event on youtube on Saturday with Aron Ra about his book, ‘Foundational Falsehoods of Creationism’. Not sure if you knew or were there.

On the first one. I will start by an examples to set the scene. If you take a scan of a foetus in the womb, then a photo of the new born baby and on through the person’s life until s/he dies, you have very different images and stages. A baby, a child, a teenager, an adult, a middle ager and an old person. We give them man-made names that we create for identification purposes, but they are still one, single person throughout. The genetic code is the same, from where we can know this. So whilst a foetus may have little morphological resemblance to the pensioner, we KNOW (can test and prove) that they are one and the same. And a photo of two foetuses or babies or people, no matter how alike they may appear, we can know that they are not the same, by the same (and other) method(s).

If we found tree-like structure on another planet that looked identical to an oak tree on earth, then it is possible that it is more similar to a rock or an elephant, because by similarity we mean relatedness. The tree from another planet would actually not even be a part of the, ‘tree of life’, because it has no place in it, just like all the aliens in film and TV, despite their humanoid appearances and they would not be able to interbreed with humans or earth life. The whole genetic (or otherwise) structure would not correspond.

And we also know that a dog, a hyena, a coyote, a fox, a wolf and a thylacine are different and why and how different, by the genes, which is really helpful when they look alike. In previous centuries, we did not have genetics, so morphology and physiology were key concepts in deciding classification.

So, whilst a baby is different from an adult in many ways, in terms of relatedness or ancestry, they are one and the same. And the biological parents are the last generation and so on. With genealogy, we (think we) can trace our parents back for centuries or more, but technically, we can’t, because if any mother had an affair, or secretly adopted or records got mixed up, we would not have a true ancestry and from the first erroneous parent, all previous ones would be wrong.

Evolution does not operate from parent to parent – this would be impossible to keep track. It works on a species or population level. This means that if an offspring is illegitimate or a parent has multiple partners and even if there is some hybridization with a different species, it doesn’t really matter, because we are only concerned with species (or things that can viably interbreed), and that is sufficient.

Due to the fossil record and many other factors, we can establish relatedness beyond the limits of genetic sampling. So, it is not really possible to take a genetic sample for things that are millions of years old due to degradation of tissue. This is when morphology, fossil order and other known or determinable factors come into play and confirm (or otherwise) one another.

So, how do we know that amphibians evolved from fish and reptiles from amphibians and creatures with internal skeletons from ones that had none? The forms can be traced in the fossil record. Whilst amphibians exist now, when amphibians first emerged, there were no reptiles. We can further trace the skeletal evolution which just so happens to exactly match the geological order. And when we test living amphibian and reptile genetic markers, it matches to that ancestry. We can therefore make predictions that if true, support this concept, and this has been done many times and is counted on when searching for fossils today. Tiktaalic was such a prediction and found what (described morphology) where (geography) and when (geologically) discovered.

Now, we are descended from animals that do not have backbones or internal skeletons. These have a term called, ‘invertebrates’. This is a helpful term used to describe that group of animals, but it is not a term used in cladistics because it has no place. Like saying person A is male, person B is female and person C is tall. We can describe people in terms of sex, height, race or interests etc. but you can’t mix it up. So, whilst we are descended from animals that had no backbones (invertebrates) we are not invertebrates, because that mixes terminology. When only invertebrates existed, they were never called invertebrates any more that they were in-circus actors. Invertebrate is a hindsight term used to look back and mention a unifying similarity. They lacked back bones just as much as they lacked the ability to act in a circus (which some people and other animals do today). So, to a circus performer, all other life is an incircus act (invertebrate comparable).

In order to talk about ancestry, we need to stick to the correct and same terminology, like for like. So, whilst many scientist will tell you that you are a fish, they are wrong, because a fish is not an actual clade. You are (in increasingly larger key clades, simultaneously) a human (Homo sapien sapien), a hominid, an anthropoid, a prosimian, a primate, a placental, a mammal and so on.

So, you can simultaneously live in your house at the same time as your street, village, town, state, country, country, region, continent etc. It’s just a matter of how specific you want to be. To your neighbour, you live at number 45. To a Japanese pen-pal, you start off by saying you live in Europe (or wherever). It’s about perspective.

So, as life is all related, we have closer and further removed relatives. We are closer related to other apes than to dogs and further removed from oak trees, but at some point, we are related and shared a common ancestor with everything and with a phylogenetic tree of life, you can find the point at which any two different species split off to form new species.

It can be termed the law of monophyly. A true clade is monophyletic, meaning that it is a nested hierarchy containing all and only those species within a point (clade node) of divergence.

In 10 million years time, our species may still be here or have died out, but our descendants, however different, will still and always be homo, apes, mammals etc. Our cladistics lineage remains and cannot be altered or5 grown out of.

In fact, we evolved from a creature that evolved an anus before it evolved a mouth (where some creatures evolved the other way round). 

So, it would be phylogenetically true and fair to say, once an arsehole, always an arsehole!

Regarding your second point.

A clade is basically a speciation event. A species is a very difficult and argued about term which is confusing to science and the world at large, because it is used differently by well informed people. This is a whole lecture on its own.

If we assume for arguments’ sake, that a species is a population of related organisms that can interbreed and have departed, genetically or geographically or behaviourally from other close relatives such that they no longer interbreed (even if they are still inter-fertile), then these are examples of speciation and would justify a new species/clade.

So note, speciation takes time and is a population (not an individual) event. Search, ‘ring species’ for an example of observable speciation.

Note also that one species never gives birth to another species or anything that is hardly any different to itself. This is what evolution predicts (to not do so would defy evolution). Imagine a gradient from red to blue. At any point, it is identical to its neighbour. You have to zoom out and compare distant places to see or notice the difference.

I hope this helps.

Thanks for your interest. There are many of us who have left fundamentalism and who were conned by Creationism. Do please joint our journey into supporting or providing a visual tree of all life, demonstrating the fact of evolution.

Steve

 

 

 

[Jaz 1]

Well put! Just as a side note, these distinctions in all the sciences (not just bio) often seem pretty arbitrary especially in small samples or close up. For instance the difference between glass and quartz, they both have a molecular structure of one silicon and two oxygen (SiO2). In glass the molecules are all over the place and in quartz they are in nice ordered rows and if your sample is absurdly small (say two molecules) then you can't tell if they are nicely ordered or if they are amorphous/unstructured thus defining the sample as either is difficult. You see the same issue when trying to determine the boundary between our atmosphere and space, how little atmosphere is needed before it can be called space.