Thread: Evolution Help for fiction

Hi my name is ttyo888, I am rather new to this forum which I believe can give me answers for some info needed for a fiction which has a lot to deal with in island evolution

I believe I can get my answers and constructive criticism here. The writing forums unfortunately do not have much realistic answers.



Info I have currently

The only problem is how or why the birds evolved into what I dream of
Here's one

Well, from the looks of your drawings (which are quite cute, I must say ), the major change from most modern birds is that they have become flightless. The ancestors of birds were of course flightless themselves, but flight has major advantages and became a big success among birds, evolutionarily speaking. I would suggest you look up other flightless birds and research how they evolved.

I'm pretty sure that the lineage of penguins goes: no flight > flight > no flight again; as for ostriches, I'm not entirely sure they ever had flying ancestors (you should look that up). That would help solve part of your problem, if the ancestors of your little guys are a side-branch of birds that never evolved to fly to begin with.

However, I'm also pretty sure that the dinosaur ancestors of birds were all bipedal (you can look that up too). Your little guy looks largely quadrupedal. There are a lot of differences in limb and girdle (aka shoulders and hips) structure between bipeds and quadrupeds, so making that change would be quite difficult. Even birds that have become flightless are still bipedal. And birds' front limbs have changed dramatically in order to from more aerodynamic wings - they don't just have those cute little hands hiding beneath the feathers.



I think the biggest advantage quadrupeds have over bipeds is in balance. This is why quadrupeds tend to be better climbers. But if you need to be up high in things, why evolve to climb when you can already fly?

If you want to keep your little guys as they are, I think the most realistic option is to say that they are descended from a side branch of quadruped, beaked dinosaurs. That became quite social and intelligent (judging by the round, big-brained head like parrots have), and largely eat seeds (judging by the beak). If they eat seeds then their little hands might have evolved to help manipulate the seeds and/or climb up in trees to get them (like squirrels and other rodents). In this case though, I'd suggest you drop the little stunted flight feathers on the arms and tail, because neither they nor their ancestors would have needed them.

To add, perhaps apropos, to Paralith's excellent response - the only modern bird I know of with claws on the front limbs is the Hoatzin - where the fledglings have them and which helps them, it is assumed, in crawling over branches/back to their nest. The adults lose these claws.

Penguins I suspect have the most 'functional' non-flight front limbs - they use them not just for swimming ('flying through water', is the usual description) but also as aids to clambering over rocks, up ice faces and so on. Their feathers are furlike too, but, as Paralith suggested, unless you propose to use them for sexual selection purposes, the stunted flight feathers are redundant and would very soon be bred out of a population.

I see

OK I did a bit of sleuthing around the net. I managed to identify the key species that will evolve to populate my island.

Basically, the area I posted in the Google Earth pic earlier. Has the following based

Tubenoses, a lot of them
Frigates
Skuas from Antarctica
Gulls
Terns
Lorikeets
Pacific Black Duck= in the past they had giant tree-browsing cousins in Hawaii.

Swallows
Old World warblers
Monarch flycatchers


This is based on the avifauna of the French Polynesia but excluding the ones that are introduced by humans.

I can say that it's a case of well convergent evolution and adaptative radiation.

But what kind of conditions will tempt a bird to give up flying and start moving on fours?

Originally Posted by ttyo888

But what kind of conditions will tempt a bird to give up flying and start moving on fours?

Lack of ground predators.

In New Zealand bats have gone back on the forest floor and hunt like ancient shrews, not using their wings.

Btw. although there is the dogma that evolution cannot go in reverse, there are actually examples of this actually happening.

but I am too lazy to look it up. And I can't remember from memory.

Could you define what you mean in this context by 'in reverse', spurious?
We know there are instances where organisms become less complex - whether you define this from a morphological, or genetic point of view.
There are other case where animals return to a former lifestyle - whales would be an obvious example. I suspect you are meaning something else.

Dollo's law, as it is known, should really be known as Dollo's rule-of-thumb

it just states the fact that there are so many different pathways evolutionary change can take that once evolution has taken a certain route, it is very unlikely that on a reversal you'll end up with exactly the same end product as you started of with

e.g. if horses started living in forests again, i'm sure they'd go smaller again than the present Equus caballus
in the end they might even look a bit like Hyracotherium in general shape, but i doubt very much that would be exactly like Hyracotherium

One reason for a bird to become flightless might be that they become too big to fly. The weight goes up as the cube of the linear dimensions but the wing area and bone strength go up only as the square. Maybe there is a kind of seed on the island that is too big for the smaller birds.

Originally Posted by Ophiolite

Could you define what you mean in this context by 'in reverse', spurious?
We know there are instances where organisms become less complex - whether you define this from a morphological, or genetic point of view.
There are other case where animals return to a former lifestyle - whales would be an obvious example. I suspect you are meaning something else.

Violations of Dollo's law.

examples:
Modern lynx have two sets of lower molars. In the fossil record felines have lacked the second molar since the Miocene. A lost tooth has reappeared.

Snakes: ovipary could have re-evolved.

stick insects:
wings have re-evolved

It seems that at least developmental modules can re-appear in evolution after they were once lost and be functional once again.

Could wings turn back into claws?

why not?

You can actually transform the identity of limbs by transplanting a tiny part of the future limb to a different region, from hind to front or vice versa, or between species.

For teeth you can change the identity of a tooth by changing either the epithelium or mesenchyme depending on the stage.

A friend of mine actually once created teeth in a chicken by replacing the neural crest cells of the chicken with that of the mouse. The avian oral epithelium is therefore perfectly capable of making teeth, although they lost the ability 80 million years ago, but is merely lacking the proper signals which could be very simple.

http://www.pnas.org/cgi/content/abstract/100/11/6541

Originally Posted by spuriousmonkey

Originally Posted by ttyo888

But what kind of conditions will tempt a bird to give up flying and start moving on fours?

Lack of ground predators.

In New Zealand bats have gone back on the forest floor and hunt like ancient shrews, not using their wings.

So actually I should have said:

Lack of ground predators and an abundant food source on the ground combined with good nesting opportunities near the food source.

You could see it as a logical exercise really. Why do birds fly?
1. safety
1a. escape from predators
1b. reaching safe nesting areas

2. travel
2a. search for food
2b. migration during seasons
2c. search for a mate.

If there is no need for any of these then the energy factor comes into play. Flying costs a lot of energy.

Radiation from the test site had an ill effect on the little critters food source so they were forced to take to the floors to hunt for a new type of food. Due to the dangers still present on the forest floor they found it alot better to hunt during the night and that is the reason for their lovely big eyes. As for their rather tubby bellys maybe their new food was a rather fatty grub :P .

Spurious - what do you think about going from bipedal to quadrupedal? I thought that would be more difficult than simply going flightless, considering the changes in limb structure involved.

there are obviously examples of certain types of dinosaurs that have reverted from a bipedal to a quadrupedal stance

however, i'm not sure whether this route is still open to birds : their special way of folding their wings may prevent it from being used as a load-bearing member

the closest birds or bird-like dinosaurs have come to giving it a different function was Mononykus, but even that one was bipedal

Hey how about this theory about why some of my birds are walking on fours...

The island was once covered in rainforest like hawaii so it was difficult for mammals to reach and birds of prey to spot anything edible except bugs.

IN fact for a long time, bugs dominated this islands. Something like the Weta-sized bugs being the dominant predators of the island until seabirds evolved.

Then they find this lush rainforests full of unexploited opportunity. Did I mentioned that seabirds are opportunists? Enough bugs to keep the chicks well fed, the climate was pretty stable, well some decided to stay.

But being a thick forest, it's pretty crowded and food alway hiding in holes. And seabirds lack the perching toe of passerines so they can't perch. So they needed to climb trees though to get a sudden glut of food mostly bugs.

Then a mutation came into being, the birds developed claws to climb trees and shrank to fit their new homes and also it helped lot in evading Skuas.

Then of course food in the ground is plentiful too. and birds have to manuveur in the ground to burrow to seek that grub.

Whatathink?

Originally Posted by paralith

Spurious - what do you think about going from bipedal to quadrupedal? I thought that would be more difficult than simply going flightless, considering the changes in limb structure involved.

As I have said before. Some bats have done it and don't seem to be hindered that much by having wings attached to their front legs.

The problem with birds is that they don't seem to have a need to walk on four since they seem quite adapted to walking on two.

The only scenario I can think of is that the wings were first used just to lean on. But why the fuck would they do that?

Then there is the scenario that birds had to evolve to climb. Maybe it did become better to have little claws on wings and haul themselves up. But they have wings, so they could just have flown.

So you are looking at a complex scenario that involves multiple steps of directed evolution.

Loss of flight.

re-adaption of wings.

Now the question is do you really need to know how they did it?

For many current structures we can only guess at their evolutionary path. Why explain something at all?

Just make sure something is functional and adequate.

Yes but a lot of seabirds are clumsy on two and some like Albatrosses, it's looks very clumsy and embarassing when walking or landing!

See the Life of Birds for info, I got only up to episode 2 when they show an albatross landing. Ha ha ha, it had to use its wings to help it stand up again!

The swallow family most of them have feet that are for perching and not walking so they hinder a bit in walking.

And unlike the European Robin with friendly humans and pigs digging out grubs for you, the birds here most likely have to dig for themselves. And like the New ZEaland undergrowth, where bats are foraging on the ground. I suppose that would work well wouldn't it.

And another thing important is that their backbones will become unfused as they become more adaptated to foraging in the ground and the trees. But unfusing the backbone is still plausible right?

Hey here's some of the beak shapes I can conjure up but is it possible to have such weird beak?

yes
http://artfiles.art.com/images/-/Roy...C12000979.jpeg

Cool the shoebill? Wait the lower mandible has a talon like mine right?

No, but other birds have them. It is well within the range of what is morphologically possible.

Concerning how birds would go from flying to climbing, isn't it possible that the rainforest they live in could be incredibly dense with branches and leaves a meter above ground or so? I can imagine how climbing would be more advantageous than flying in that case.

I don't see how a rainforest could be that dense without killing each other completely from competition for resources, water, air, minerals in the ground, and sunlight. Because of the last one, there probably wouldn't be leaves anyways, so little photosynthesis, it would be best to invest in leaves at the top. Ultimately, any trend towards such density will result in such competition that such a density would never be realized. And the most dense forests of today, of course, have birds.

Well the thing is the right family of bird evolving then, because the island is frequented by seabirds like gulls, albatrosses and tubenoses and most of them having webbed feet can never perch on a tree. But with so much insect prey it would be advantageous to start to learn how to perch or learn to climb.

how about rails (rallidae) ? they're notorious for becoming flightless once they've reached an island
i think at one time nearly every island in the pacific had its own endmic species of flightless rail - something to do with an embryological disposition to make the breastbone smaller

But as it turned out the "Flightless Ostrich" body plan was a evolutionary dead end. See t-rex or the Moa and several ground dwelling species in NZ.

flightlessness usually only evolves (i'm excluding the ratites for the moment) on islands without ground predators or egg eaters

after all, flight, even though it's expensive, has its benefits, one of which is the ability to escape predators and build your nest out of reach of them

so flightlessness is a viable evolutionary strategy on an oceanic island, provided no new invaders make your niche untenable

Originally Posted by ttyo888

But as it turned out the "Flightless Ostrich" body plan was a evolutionary dead end. See t-rex or the Moa and several ground dwelling species in NZ.

The ostrich is still doing fine.

So are several other large flightless birds.

Hardly an evolutionary dead-end.

Maybe like this?

Before the birds arrived, my island for a long time appeared to be dominated by arthropods and the bigger predator maybe a Weta!

Later seabirds came and the insect and crusteceans became the bottom of the food chain.

Tubenoses and gulls find enough food to sustain their young because there were bugs to feed their young so they evolved flightlessness like ostriches and rails.
But of course tubenoses and gulls having webbed feet end up falling down.... so some took up tree climbing to access bugs hiding in the leaf litter like New Zealand bats or to extract bugs that are in trees. Losing flight is a good idea to extract the bugs.

The plants of course had Pigeons and Anseriformes eating them. They also adopted the Ostrich Body Plan but they remained small as mousedeer.

Then a new kind of bird arrived on the island maybe a predatory gull like a Skua and then those that did not take up tree climbing became defenceless to the skua-like predators and became extinct.

And later even the skuas had to change to 4 limbed to hunt the prey hiding in trees like the pine marten.

Later the cooling of the Earth, caused the rainforests to retreat. this created newer habitats to exploit. The Anseriforms in balloon to the size of mammalian herbivores. The Pigeons too got bigger.

The 4 limbed creatures which were seagulls and tubenose exploit their ancestors talents and changed to quadropeds and hunted the geese and pigeons.

Anyway, you guys are of great help. Thanks but I wonder under such a environment. Why will the Anseriforms and Pigeon adopt the Quadroped body plan?

just some eye candy I created