Researcher: Mammals evolved a large brain to accommodate a sense of smell

_{Denyse O'Leary

June 6, 2011

Evolution}

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In Ferris Jabr’s “Early mammals were brainy and nosy,” (New Scientist, 19 May 2011), we learn:

The evident importance of smell and touch to these tiny proto-mammals hints at their lifestyle. The 190-million–year-old animals probably navigated dark burrows and skittered through leaf litter hunting insects – activities greatly helped by sensitive smell and touch.

And thus they avoided dinosaurs, except that

Having a great sense of smell is also consistent with the idea these mammals may have been nocturnal,” explains Rowe. Despite recent evidence of nocturnal behaviour in dinosaurs, it’s generally thought that most of these animals were active at day and asleep at night. “That’s when the mammals came out. With a great sense of smell, it doesn’t matter if it’s dark,” he says. “Smell might be what made it possible for early mammals to come out and find food and mates. In the early Jurassic, that was what drove their evolution.

Sure.

Tenured prof: Ignore competing lines of evidence. Only boobs and creationists consider such things.

Comments

Sorry, Mung, I’m not seeing it. What inconsistencies are you seeing in my way of speaking about selection?
Your lack of consistency in speaking about selection.Mung_{June 24, 2011
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"Such an inspiring belief system." Especially when one pauses to consider that its mathematical formulation may, without loss of detail or accuracy, be expressed thusly: x + x + x + ... + x = 1 [where 'x' is some miniscule negative number].Ilion_{June 8, 2011
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I said that a brain-like thing was probably an advantage
Let's not lose sight of the fact that your "brain-like thing" is purely hypothetical. You apparently believe it existed, or you wouldn't bring it up, but where's your evidence? Add that that your "was probably an advanteage" and we've added another hypothetical, for which there is also no evidence. Such an inspiring belief system.Mung_{June 8, 2011
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My point is that is that any such phenotypic effects are, according to the theory, the cumulative results of individual mutations. If you add up a whole bunch of mutations, you might get some new feature or behavior that might get selected. But that's X-Men, and I'm sure no one is proposing that. The theory is that individual mutations get selected, they propagate, and then so on, until there is some new feature or behavior. But how does a single genetic change get selected? Does it really make an animal less likely to get killed by a predator or more likely to reproduce? Is natural selection really so specific that it carefully guards the initial stages of some random series of mutations so that it can one day grow into something new? Doesn't that attribute intelligence and foresight to natural selection? (I'm sidestepping the numerous other ideas floating about besides mutation + NS because none of them have been described specifically enough to address. Not that there are a whole lot of specifics on this one. Mutation + NS pretty much sums up what there is to say about it.)ScottAndrews_{June 7, 2011
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@ Scott Andrews:
Is this really true? Is the very first tiny mutation, the first step toward a larger brain, really going to keep it from getting picked off by an Archeopteryx? What animal gets a date because of a single mutation? If there’s a mutation to make the brain bigger, don’t we still need another mutation for the sense of smell to take advantage of it? How does that first mutation confer advantage? At least one more perfectly coinciding mutation has to happen right behind it. (Same root word as coincidence.) And the whole history of life must be based on billions of such coincidences. A theory based on that premise is fatally flawed. No one should take it seriously.
I seem to have been confusing :) I did not say that a larger brain was necessarily an advantage. In some contexts it almost certainly isn't. I said that a brain-like thing was probably an advantage (far earlier than archaeopterix, which certainly had a brain!) However, as the OP is about larger brain (my point was rather tangential) I think there are a few points worth making: there are a huge number of genes implicated in brain development. Of those, relatively few are likely to be specific to brain growth, and the vast majority are regulatory genes that modulate the not only the developmental timetable but also the way that cells develop in response to both the internal (both local and more global) and external environment. The mechanisms by which genes have phenotypic effects is fascinating, and I find myself a bit annoyed by articles like that cited in the OP. Not least phenotypic effects in a population themselves contribute to the environment within which the heritable traits that give rise to those effects are selected. It's the kind of simplistic thinking that gives biology a bad name!Elizabeth Liddle_{June 7, 2011
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Sorry, Mung, I'm not seeing it. What inconsistencies are you seeing in my way of speaking about selection?Elizabeth Liddle_{June 7, 2011
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Elizabeth @8:
No, it isn’t a “shell game”, Mung.
Well, I beg to differ, and I think your very next sentence gives yet another example of the shell game in action.
There’s nothing switchy about pointing out that anything that gives a reproductive advantage will be selected (by definition).
I think the fact that you have trouble adopting a consistent way of speaking about selection ought to give some indication that there's more here than at first meets the eye.
The term natural selection has slightly different definitions in different contexts. http://en.wikipedia.org/wiki/Natural_selection#Nomenclature_and_usage
Mung_{June 7, 2011
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If there’s a mutation to make the brain bigger, don’t we still need another mutation for the sense of smell to take advantage of it?
And what good is a sense of smell with no sense organ? It's downright miraculous how all these little genetic accidents all added up.Mung_{June 7, 2011
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There’s nothing switchy about pointing out that anything that gives a reproductive advantage will be selected (by definition).
Is this really true? Is the very first tiny mutation, the first step toward a larger brain, really going to keep it from getting picked off by an Archeopteryx? What animal gets a date because of a single mutation? If there's a mutation to make the brain bigger, don't we still need another mutation for the sense of smell to take advantage of it? How does that first mutation confer advantage? At least one more perfectly coinciding mutation has to happen right behind it. (Same root word as coincidence.) And the whole history of life must be based on billions of such coincidences. A theory based on that premise is fatally flawed. No one should take it seriously.ScottAndrews_{June 7, 2011
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No, it isn't a "shell game", Mung. There's nothing switchy about pointing out that anything that gives a reproductive advantage will be selected (by definition). That doesn't mean that what gives a reproductive advantage is "necessary", it just means it's advantageous, in that population, in that environment. And no, simply contributing to survival does not guarantee reproductive success, which, as you point out, is what matters. But surviving to maturity is certainly a help when it comes to leaving offspring. Darwinism may have its flaws (indeed it doesn't account for some phenomena) but this certainly isn't one of them. If you think it is, then you definitely have a straw man there!Elizabeth Liddle_{June 7, 2011
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No, it doesn’t follow, true, but having a brain is quite useful for leaving more offspring.
Except when it isn't. http://www.darwinawards.com/
What isn’t logical is to assume that because something isn’t necessary for survival, that having it wouldn’t help.
But no one is saying that. So...
Tea isn’t necessary for survival, but it sure helps….
Everyone notice the switch? We're all of a sudden starting talking of survival rather than reproductive excess (leaving more offspring). This is part of the shell game that Darwinists pull all the time. If it's not useful for leaving more offspring then it hardly matters, from a Darwinian point of view. Even if something contributes to survival, it does not logically follow that it increases reproductive success.Mung_{June 7, 2011
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No, it doesn't follow, true, but having a brain is quite useful for leaving more offspring. Darwinian evolution is nothing if not logical - it is simply the statement of the logical truth that if something replicates with variance, and the variants vary in their reproductive success, the variants better at replicating will become more numerous. And so, if a brain-like thing increases reproductive success, then that lineage will tend to thrive. My own theory is that the origins of brains are related to the origins of mobility in multi-celled organisms. When you can move, it hugely helps to be able to predict what is likely to happen next, and how moving can either make it more likely (in the case of something nice) or less likely (in the case of something nasty). What isn't logical is to assume that because something isn't necessary for survival, that having it wouldn't help. Tea isn't necessary for survival, but it sure helps....Elizabeth Liddle_{June 7, 2011
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And clearly having a brain is quite useful
From which it does not follow that having "a brain-like thing" leads to leaving more offspring than others of your kind. But then, logic was never required by Darwinism either, for that would require a brain, which as we all know, isn't necesary for surivail.Mung_{June 7, 2011
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Brains are not "necessary for survival" - many living things do not have brains (e.g. plants). The issue is whether a brain-like thing in a lineage provides that lineage with a survival advantage. And clearly having a brain is quite useful :)Elizabeth Liddle_{June 7, 2011
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This is just silly. Do they even do the thinking necessary to do science? It appears as though they're allowing their metaphysics to do their thinking for them. I've always wondered why the brain and the sense of smell are even necessary for survival. One would think that if Darwinian evolution were true, microbes would have been fine without evolving into us or anything else.CannuckianYankee_{June 6, 2011
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If smell/sight etc is the origin of big brains then why is intelligence associated with big brains.? indeed perhaps bigger brains do just accomadate non thinking needs. Yjis means there is no reason to conclude dinos or the early mammals were in any way dumber. they simply didn't need added help. In fact as a yEC creationist who sees the k-t line as the flood line and aware they say the 'first' mammals above the line always had smaller brains it follows this could be because there was not a need to search about more for food. it was because the world became less diverse in the fauna that creatures in a minor way ot bigger heads for minor needs of the senses. No evolution of dumb to smart.Robert Byers_{June 6, 2011
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Smell might be what made it possible for early mammals to come out and find food and mates.
One has to wonder how they found their mates before that.Mung_{June 6, 2011
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