No transitionals

Evo News has yet another article on the failure to find ‘transitional fossils’.

Since I’ve been reviewing and condensing old blog into new blog lately, I’ve acquired a feel for the strata of my viewpoints. There aren’t any transitional fossils in this record either. When I crystallize a new understanding, the viewpoint shifts abruptly.

A similar pattern happens in changes of skill or technology. When a new way of making a telescope or a gun or a radio appears, the industry gradually adopts it.

Telescopes go from alidade to lens in one step, carriages go from horse to engine in one step. There are no telescopes with half lenses, no carriages with 20% of a horse and 80% of an engine.

Some companies continue making the old (living fossils), some make both old and new, and some new companies start fresh with the new.

It’s the same with new ways of composing music or art or literature. The new either takes over or fails. The old continues in some places, and often reaches new heights of perfection just before it collapses. But there are no transitional fossils.

We know how these sudden jumps happen in our own learning and technology. The change happens in MINDS, and even within the MIND there are no transitional neurons. Some sections of memory or limbic system remember the old, just as some companies continue building the old. The sequencers in the cerebellum archive the old skill or the old song, which remains available forever in case the new fails.

But where is the MIND that creates the shift in animal phyla and species? Is the God Studio an itinerant, checking in on various planets from time to time and implanting new genomic ideas?

Katydids part 1, reprint

I wrote this item in 2012. A new piece of related research spurred me to revise and expand. First the 2012 version:

= = = = = START REPRINT:

Wonderful example of what can happen when you decide to look closely at something, instead of fucking around with numbers and potentialities and apocalyptic religious delusions. In other words, when you do ACTUAL FUCKING SCIENCE.

Katydids are thoroughly familiar insects. We’ve all heard them, seen them, probably handled them or batted them away when they jumped on us. We knew that they made sounds with their legs, and that they somehow heard with their legs.

Now someone finally decided to look closely, with amazing results.

A team at Lincoln Univ in Britain used electron microscopes to examine the ears, which are inside the front pair of legs.

I’ve done a 3d pic and animation based on their descriptions.

Each of the front legs has a pair of tiny openings. Behind each opening is a tympanic membrane, much like ours.

I’ve shown one side of the leg here. Each Tympanic Membrane (eardrum) has a ‘plate’ or lever on one edge, serving as a leverage multiplier like our Ossicles. The plate transfers the wave motions to a fluid-filled Acoustic Vesicle, which plays the same role as our Cochlea. The Vesicle picks up the waves from both drums in this leg. It contains hair cells that wave back and forth, sending neural signals to the katydid’s brain. Fluid inside the Vesicle is a dense version of the insect’s blood, again just like the fluid in our Cochlea; and the hair cells are tuned for different frequencies, just like ours.

Eardrums need to avoid being moved by changes in atmospheric pressure, which can be much larger than sound pressure. Mammalian ears balance the pressure on both sides of the drum via the Eustachian tube that opens into the nasal passages, insuring that the middle ear chamber stays at the same pressure as the air outside the skull. The katydid solves the same problem with an Acoustic Trachea, a tube running up the leg, into the body, and thence into one of the insect’s ‘lungs’.

When sound impinges, each eardrum transfers its energy to a ‘pinch’ on one side of the Vesicle.

Aside from the pairing, there’s only one major design difference between mammal and katydid. The katydid’s paired eardrums push on the side of the Vesicle, while our eardrum pushes on the end of our cochlea:

= = = = = END REPRINT.

Katydids part 2, revision

New research at Bristol takes a closer look and separates out the parts more clearly. So I’ll do the same.

First we see Katy walking along a branch, and pausing when she hears something interesting…

What does she hear?

Perhaps something in the air, or perhaps a vibration on the stem that indicates a tasty insect at work or a matable male singing Our Song.

Where are the ears?

On the second joint of each front leg. Each leg has two eardrums facing roughly 90 degrees apart.

Here’s a transverse view of the joint in the same position. The Crista is the framework that holds the sensory hair cells, and merges their signals into a cable leading to the brain. The trachea is actually divided into two parallel pipes, and each tympanum pushes on one of the pipes. The trachea ultimately runs into one of the spiracles (lungs) on this side of the abdomen. Most likely the trachea serves the same purpose as our Eustachian tube, equalizing major changes of pressure so the tympanum can move more freely. Some researchers think the trachea is the main inlet for sound, but this seems unlikely.

How do the two tympani respond to waves in the air? Here we have a major difference. Our eardrums are at the end of a canal, so sound from all directions is narrowed down into a single inward-moving wave.

Katy’s tympani are fully exposed, with their length parallel to the row of sensory haircells. So the sensing organ can read the direction of sound.

The row of 50 sensory cells is tuned just as ours is tuned. The cilia at one end are shorter, and the cells are smaller, so they will respond to higher frequencies.

Most of the tuning in our cochlea is done by resonance within the fluid. A mix of frequencies is coming in via the tympanum, and the various harmonics and formants bounce through the chambers differently.

Some frequencies form a traveling wave, which runs through the chambers with no net force at one point:

And some frequencies form a standing wave at one location, giving strong motion to one group of hair cells:

Here’s a cross section of our cochlea while it receives a standing wave. We also have two parallel tubes, but they aren’t sensing two sides of the universe; they’re just carrying different types of fluid. Unlike the katydid, we have two separate groups of haircells. The inner cells (left here) are the actual sensors. The outer cells (right) are effectively muscles, exerting feedback counterforce on the upper membrane to damp down steady or uninteresting sounds.