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Morels are among the most desired edible mushrooms as well as the most mysterious. The mystery stems largely from yeast-like characteristics. The morel maintains a physiology similar to yeasts because of its very recent evolution from a yeast.

Here is a general description of morels:

Morel mushrooms have an unusual appearance, because they produce ascospores,  which means the spores are enclosed within the tissue, and a force propels them out. The spores must therefore be near the surface, and a lot of surface area is needed. So there are ridges on the surface

Morels, however, are nothing like sponges. They are hollow, rubbery and  brittle—much more brittle than other mushrooms. In fact, mushrooms usually have a tough skin over the surface and a fibrous stem. This prevents pieces of mushroom tissue from breaking off. By contrast, morels crumble easy and are often broken—an inadequacy stemming from recent evolution from a yeast.

The cap of the morel has many inadequacies which other mushrooms overcame. A typical mushroom cap protects spores from being washed away by rain. The morel cap does not. The gills of mushrooms have aerodynamic properties for exploiting wind. Morels cannot use wind nearly as effectively.

In other words, the use of ascospores by the morel was not a result of advantageous evolution but a disadvantageous carry-over from a yeast.

Creating a practical growing procedure for morels has been a long term task in science. The first assumption is that they should do what other mushrooms do. They do not, because they are nothing like other mushrooms.

Mushrooms are usually decay organisms. They produce enzymes on the surface of the mycelium for breaking down large molecules. Morels do not, except perhaps for attacking some polysaccharides, as yeasts do.

Mushrooms are usually quite ancient in their evolution, which makes them hardy and easy to handle, as difficult as mushrooms can be to handle. Morels are in the infancy of their evolution, which makes them very fragile to handle.

But there is more than recent evolution to the difficulties in controlling the growth of morels. Being the physiological equivalent of yeasts, morels are not well adapted to the soil, as mushrooms usually are.

Morels may seem to be ubiquitous, but they are environmentally fragile, and they do not disseminate well, as explained in the summary.

The dissemination problem combined with rapid evolution resulted in morels varying in their appearance from area to area. Morel types are so variable that nomenclature is in a state of confusion.

The largest division is between brown and black morels. However, the browns blend into whites, with yellow or tan morels in-between. The blacks also do not create a sharp break from the browns, as various types of grays are in-between.

Morels are also highly variable in size and shape. Cylindrical to cone shapes are perhaps the most common. Totally round morels are not uncommon. Pencil shaped morels are more rare.

Ice Age Theories:

The morel mushroom provides evidence on the cause and characteristics of ice ages.

Evidence indicates that the morel re-evolves at the beginning of each ice age. High humidity and rainfall are probably required to start morel evolution, because a filamentous yeast must resist dehydration on tree bark during the early stages.

There are places where humidity stays high routinely; and therefore, there is a question of whether humidity needs to be any higher when the morel starts its evolution. However, a truism is that unusual conditions promote major steps in evolution.

When considering these points, morel evolution creates the impression that ice ages start with high humidity and rainfall. Other theorists, however, have been assuming that ice ages start with dry and cold conditions and continue that way until the reversal starts, which takes about 80 thousand years.

One of the most recent theories about the cause of ice ages is that the earth's orbit moves to the edges of its plane at exactly the time when ice ages occur; and out there, the earth's atmosphere picks up dust particles which cloud the air and cool the whole planet.

I find three major problems with that theory. One is that the earth and solar system move continually and influence other masses by their gravity. Why then would dust particles follow the earth without changing their positions? Comets demonstrate that nearby particles are moved around by such factors as solar winds.

Another problem with that theory is that ice ages have only been cycling at 100 thousand year intervals for the past million years, but they continue back in time at other intervals for about a billion years. So most ice ages have not been cycling with the earth's orbit.

Another problem is that the theory requires a trigger concept which says that the ice age is self-generating after it gets started. Otherwise, it would not proceed for 80 thousand years before reversing. But self-generation does not add up. When the air got dry and clear, warm up would start the reversal, and the cycles would be very short.

My theory for the cause of ice ages is that one or more hot spots in the earth's core moves around and comes closer to the surface from time to time. When near the surface, it heats the oceans causing more rain to occur. The increased rainfall causes snow to accumulate faster than it can melt. The increased snow and the cloud cover reflect sunlight causing a cool-down of the planet.

With this theory, the reversal can be attributed to the movement of the hot spots in the earth's core. The reason why ice ages increase 80% of the time and decrease 20% of the time could be that the earth's surface is slow at responding to warm up but fast at responding to cool down.

An explanation for the large variations in the cycle time of ice ages is that the movement of tectonic plates could cause oceans to heat differently, or the movement of hot spots in the earth could be variable.

Finally a possible explanation for the evolution of morels is that a suitable environment is created in front of the ice sheet which covers part of the northern continents during an ice age. Cold air sweeping off the ice may prevent summer heat from dehydrating the yeast which evolves at the base of trees, as it adapts to the soil.