Could mammals have evolved from birds?

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It's is believed by scientists that they came from reptiles, but could they have come from birds? A primitive mammal, the platypus closely resembles a bird. It can lay eggs. Could hair have evolved from feathers?

Birds and mammals come from a prior common ancestor.

We are all descended from swamp muck.

ruveyn

Evolution isn't linear. Avian and mammalian creatures are separate branches of the tree.

Noooo... Birds came from dinosaurs, and mammals branched off from reptiles before there were birds.

Mammals evolved from Synapsids which were considered mammal-like reptiles. They existed contemporaneously with Archosaurs who further evolved into Dinosaur phyla as well as Avians. The last remaining Archosaurs are crocodiles and their relatives alligators, caimen and gharials

I thought science has shown that both birds and mammals most likely came from reptiles? If both evolved from reptiles it isn't surprising that some mammals like the platypus have bird and/or reptilian characteristics.

Many of Australia's animals, such as the platypus, are endemic and have experienced a long period of evolutionary isolation. Thus they diverged a long time ago and represent very old genera. I'm not totally sure whether platypus lay eggs due to ancestry or via convergent evolution. Monotremes such as the platypus are not that well understood compared to other mammals

All of the genetic data we have so far suggest that birds share a common ancestor with the rest of the reptiles more recently than they do with mammals, which had already branched off.

The most recent common ancestor of mammals and reptiles was almost certainly egg-laying, so it is probably a result of ancestry rather than convergent evolution. The monotremes simply split off as a separate lineage before the placental mammals started giving live birth.

And the root of the tree is unicellular slime.

ruveyn

Folks dont realize that mammals and dinosaurs were contemporaries who both appeared at about the same time in the fossil record, but evolved from different groups of reptiles.

The mammals became the supporting actors taking the role of small nocturnal insectivors while the dinosaurs took the starring roles as all the large diurnal herbovors and carnivors ( brontos and t-rexs) - which is why the dinosaurs steal the show during the mesozoic.

Mammals had already been around a long time when the birds branched off from the dinosaurs.
Not only is the chronology wrong but anatomically the two groups show their differing pedigrees- mammals have very little anatomically to connect them with birds, in contrast to the way that birds do have many archesaurean and dinosaurian traits.

Also: for birds to have spawned mammals they would have had to reevolve fore legs out of wings( it was hard enough to turn dinosaur forearms into wings in the first place).

So no. Mammals could not have evolved from birds.

The egg laying by the platypus is obviously a retention of the practice of egg laying from its (and our) reptilian ancestor that weve lost, and not a latter day reinvention.

Our dinosaur-era primitive mammal ancestors retained egg laying for a while even after becoming furry mammals (like the platypus) before we moved on -first to the pouch idea ( still retained by marsupial possums and kangaroos) before finnally becoming the full fledged placental mammals that we are today. All of this occured during the hundred and fourty million years that mammals lived in the shadows of the dinosaurs. A period longer than the 63 million years that the mammals have dominated the planet since the dinosaurs.

just to note, that mammals evolved from primitive reptiles of the time. Probably looking superficially like modern reptiles, but still laying soft eggs in water like amphibians. I don't think theres anything like that surviving today. Our ancestors never layed hard shelled eggs like modern reptiles.

I'm not sure this is true. The taxonomists who insisted on the inclusion of birds within reptiles (to avoid paraphyly) did not advocate putting mammals inside reptiles.

What? I don't understand why you respond the way you do. Taxonomists? mammals into reptiles?

The theory goes, more or less. These primitive reptiles where dependent to water pools to reproduce. The ancestors of modern reptiles solved this by developing hard shells. The ancestors of mammals developed sweat glands in order to sweat on the eggs that they where laying on. These sweat glands started excreting nutriments that where absorbed by the eggs, eventually evolved in too ..... boobs. At that point the mammal like reptiles definitely became reptile like mammals, .... by definition. So i'm sure this is true.

OK, I should be more clear: it is not appropriate to refer to the most recent comment ancestor of reptiles and mammals as a "reptile." The set of organisms that contains all modern reptiles (including birds) forms a monophyletic clade, and the mammals had already split off before the most recent common ancestor of all modern reptiles lived. Unless our current phylogenies are mistaken, it is incorrect to say that mammals evolved from reptiles.

you're dead wrong and rather confused.

The amphibians were the ones dependant on water to reproduce because their offspring had to go through the tadpole stage in water.

The whole point of being a reptile was the innovation of egg laying that enabled the offspring to develop in a hardshelled little container away from water. That plus having watertight skin on the adult animals. So the first reptiles were by definition already free of the water, and already layed modern bird like eggs. So the ancestors of all reptiles, and all the creatures who later descended from reptiles (dinosaurs, birds, and mammals) were fully functioning egg layers. So what you're saying here isnt even possible, and its virtually the opposite of the truth.

So when the reptiles branched off from the amphibians those innovations freed the reptiles to invade the dry land, and to fan out into varieties.

The boldest pioneers to exploit this freedom from water to venture onto the land were the synapsids who became "the mammal-like reptiles". These were full blown egg laying reptiles who also had also adopted mammalian traits (like specialized teeth). The very group to most exploit the advantages of egg laying were the very linneage of reptiles that become mammals.
Some became as big as rhinos. They dominated the planet for some fifty million years.
But they were finally overthrown by the archosaurs (alligator-like reptiles) who later evolved into the dinosaurs.

The mammal like reptiles were all driven to extinction - except the few who became highly specialized to escape the dinosaurs through minaturization and by becoming nocternal.

These minaturized nocternal synapsids were forced to grow fur and become warm blooded (ie forced to cross the line from being mammal-like reptiles into becoming true mammals).

But in the beginning these first mammals probably still layed eggs like the platypus does now because their reptile ancestors had already been laying eggs for a 100 million years. So we almost certainly did go through a LONG "egg laying" phase.

Watertight skin evolved first, its relatively simple, its just a barrier. An egg however its more complicated, it has to be sealed without suffocating the embryo, and being able to hatch. So at some point you had reptile like creatures, that had to lay there eggs in water like an amphibian would. I'm not going to split hairs about what is the definition of a reptile. These were intermediate forms between amphibians and reptiles/mammals, today totally extinct.

Basically Orwell says something similar when he talks about the phylogeny (but he uses jargonese).