Bilateral symmetry (biology - higher lifeforms)

[Philosophy Explorer]

Higher lifeforms - including primates, human beings, fish, birds, reptiles - have brains and exhibit bilateral symmetry. I can give all sorts of uses for bilateral symmetry (e.g. seeing things in three dimensions, lifting up things and walking). But a deeper question looms. Could bilateral symmetry be a part of the theory of evolution? Also is there anything better than bilateral symmetry which helps a species to survive?

What do you think?

PhilX

[Logicus]

We have nothing to compare our evolutionary data to, if we would like to know if another sort of body plan would work better or not. If you are curious why this plan seems so built-in to our evolution on Earth, it came about, as I understand it, as a result of the Cambrian Explosion.

During this period, every body plan on Earth was developed and passed on through the evolutionary chains to the present. The fact that it was so successful argues in its favor. We need an alien world with a very different evolutionary makeup before we can make comparisons between bilateral and non-bilateral advantages/disadvantages.

[A_Seagull]

The reason that you have bilateral symmetry is that God did not want you to walk with a limp.

[Philosophy Explorer]

The reason that you have bilateral symmetry is that God did not want you to walk with a limp.

Yet bilateral symmetry isn't perfect. A mirror closeup would show differences between the two halves. I feel that this is a work-in-progress as nature hasn't decided which form would be most suitable, even though nature seems to favor bilateral symmetry for higher lifeforms (still we have competing amoeba).

PhilX

[DarwinX]

The human form is made up of cells and cells are made of smaller units of viral forms. Viral forms are made of symmetrical carbon chains. Bilateral symmetry is a result of chemical processes which are also symmetrical. Life forms are carbon based, and therefore, will take on the characteristics of the carbon atom. The carbon atom can form a double bond with another carbon atom, thus, we have the separation structure of the cell itself. The double bond splits into two single bonds and we have the reproduction cycle in miniature.

[Rilx]

Yet bilateral symmetry isn't perfect. A mirror closeup would show differences between the two halves. I feel that this is a work-in-progress as nature hasn't decided which form would be most suitable, even though nature seems to favor bilateral symmetry for higher lifeforms (still we have competing amoeba).

It doesn't need to be perfect. Bilateral symmetry is moving animals' adaptation to the gravity on earth. Not like amoebas which move by continuously changing their body structure, bilaterally symmetrical animals have stiffer structure (e.g. bones) to support their more complex organisms. For a perfect bilateral symmetry to evolve, it should be advantageous to move only perpendicularly to gravity (forward, backward, up and down). But in a 3-dimensional world it's better to be able to move in all directions.

For non-moving beings like trees radial symmetry is more advantageous than bilateral symmetry, so their genetic structure is radially symmetric. Local circumstances like prevailing direction of sunlight can naturally strenghten some side.

[A_Seagull]

The reason that you have bilateral symmetry is that God did not want you to walk with a limp.

Yet bilateral symmetry isn't perfect. A mirror closeup would show differences between the two halves. I feel that this is a work-in-progress as nature hasn't decided which form would be most suitable, even though nature seems to favor bilateral symmetry for higher lifeforms (still we have competing amoeba).

PhilX

So you do walk with a limp?

[Philosophy Explorer]

(Nested quote removed.)


Yet bilateral symmetry isn't perfect. A mirror closeup would show differences between the two halves. I feel that this is a work-in-progress as nature hasn't decided which form would be most suitable, even though nature seems to favor bilateral symmetry for higher lifeforms (still we have competing amoeba).

PhilX

So you do walk with a limp?

Don't know if you're joking, but no I don't walk with a limp.

PhilX

[Fooloso4]

Philosophy Explorer:

Could bilateral symmetry be a part of the theory of evolution?

Are you asking whether bilateral symmetry will always arise in an evolutionary system? It seems reasonable to assume that other natural histories would be similar to our own in that symmetry and patterns will arise and be replicated. Bilateral patterns are one of the simplest patterns, so bilateral symmetry seems likely.

Also is there anything better than bilateral symmetry which helps a species to survive?

Since there are organisms that survive without bilateral symmetry and even some that do not display any symmetry, such as some species of sponges, whether there is or theoretically could be anything better for survival would depend on the environment.