Expert: Dana Krempels, Ph.D. - 7/31/2007

Question
QUESTION: Hi,
I'm doing research on biological identity and wanted to clarify whether different humans cells can be considered Homo sapiens themselves? To me Homo Sapeins is a colonial organism with a life cycle that includes a single cell stage. Therefore only the zygote and the colonial stages are Homo sapiens, while individual cells sex, skin and blood cells etc aren’t Homo Sapiens.

It would be helpful if phenotypes regarding Homo Sapiens was also cleared up.

I’ve also had it put that cells themselves are considered just another phenotype of Homo Sapiens, so just as gender or a human with blonde hair are phenotypes so are zygotes or sex cells phenotypes of Homo sapiens. To me this doesn’t make sense, there may be phenotypes of types of cells but to conflate that with phenotypes of Homo sapiens runs into the same problem as above.

Can you help clear this up?


ANSWER: Dear Simon,

I don't know any biologist who would classify a single cell from a Homo sapiens as a Homo sapiens.  Even a zygote, which may have the *potential* to become a Homo sapiens, but is not an organism by any stretch of the imagination, is not considered an individual Homo sapiens by any members of the scientific community that I know.

A colonial organism is defined as one being composed of loosely organized cells, sometimes with a division of labor.  In many truly colonial organisms (e.g., Volvox; some would include sponges), the cells can survive on their own, when taken out of the colony, and even undergo mitosis to produce a new colony (without the help of cloning technology).  So in the strictest, biological sense, no eumetazoan (including a human) is a colonial organism.  

An organism that exhibits *true multicellularity* (as opposed to being colonial) is defined as one composed of various types of cells that are coordinated to perform particular functions by organizing into organs and organ systems.  The individual cells cannot survive for long outside the whole organism.

I do not believe the scientific community in general considers a zygote, blastula or gastrula containing the human genome to be a Homo sapiens.  To a biologist, those cells or conglomerations of cells have only the *potential* to become human.  This may be a matter of debate in social and political circles, but not in serious scientific ones.

I'm not sure who said to you that individual cells are simply phenotypes of Homo sapiens.  That person may have had a limited understanding of general biology and genetics terminology.  

An individual cell may *express* a certain phenotype, as directed by its genome (for example, a cell in the Islets of Langerhans may be "wild type" and have the ability to produce insulin, or "mutant" and lack that ability; each of those is a phenotype that is expressed at the cellular level, and has phenotypic consequences in the whole organism), but they are not phenotypes unto themselves.

Does that help clear things up at all?  Hope so! :)  Please write back if I haven't been clear enough.

Dana

---------- FOLLOW-UP ----------

QUESTION: Hi Dana,
Thanks that clears the colonial context, but I’m not sure where to take this, as my approach is coming totally out of left field.

I wrote up a response but it came out as a full page.
Unless you have time to discuss this in a little more detail I'll spare you my response:)

Thankyou you have cleared a few things up though.
Warm Regards
Simon
Ps A quick skype chat would be cool to see what you think of my idea

ANSWER: Dear Simon,

I'm such a clueless Luddite when it comes to chat that I wouldn't subject you to that.  But please feel free to send me your long response.  It's an interesting topic!

Dana :)

---------- FOLLOW-UP ----------

QUESTION:

Dear Dana,
I accidentally deleted my page but I’ll take another angle anyway. What it is to be a self replicator/ or self assembler? It is a bit longer but I hope no too long.

With the advent of micro machines and the concepts of self replicators and self assemblers I thought I’d have another look at what it is to be a Homo sapiens when it comes to signifying identity.

Imagine we have a small micro machine that is hardwired to become a larger multi modular mechanical entity. The modules are equivalent to our organs and the micro machines are equivalent to our cells. This also includes differentiated micro machines.

The larger multi modular/micro machine may have an additional functions –apart from self assembly- say as a exploratory robot and the fact it can self replicate.  The function isn’t important but for the purpose of classification it has multiple primary roles: build its fully develop stage, explore the landscape, replicate other robots by generating other primary initiator micro machines.

Now if I want to classify this thing via function yes one could argue an important  signifier is that it is an exploratory robot. But to my mind that isn’t the full story for we only have to compare it to current robotic exploratory craft that are neither made up by smaller micro machines, don’t self assemble or replicate. If the classification of the  micro machine explorer was just about being an explorer, classification wise the two machines are identical. But that obviously isn’t the case there are fundamental differences in the classifying characteristics of these two machines.  

Nor does looking at the machine at different developmental stages signify that it is fundamentally a different entity. Design function and organisationally it is the same mechanical entity. Whether it is in its initiator single micro machine stage, main building phase or completed stage it is still the same entity.

I think any account of a self assembler -especially one that is locked into assembling itself and only itself its identity –means its identity is continuous and is constrained via the same criteria that animals meet as discussed by John Locke with bodily identity.  

Would that mean other micro machines within this entity are also identified as being self assembling exploratory robots? I think not.

As we have made the machine as similar as we can to a Homo sapiens I think we would have to consider for those machines that have the full functional blue prints within them –not the highly differentiated that either have no plans or have the plans chopped up i.e. blood cells etc- the purpose of these micro machines- after the initiator- is to belong and function within the large machine. That is there designated role. Arguments about potentiality are beside the point, the original micro machine is a self assembler its role and function is to develop its organisation into its more complex stages. In principle yes you could take a differentiated micro machine and start it cloning but if we take what it requires to currently create a clone from the nucleus of a skin cell and an empty egg you have effectively destroyed the original skin cell and have just inserted the blueprint in the potential initiator shell.  The skin cell didn’t have potential it was rather the plans in the nucleus.

(On a similar note I’ve always wanted to ask what species classification does an ant hold within a ant colony super organism? Functionally and organisationally the individual ant has no identity without the colony so there could be an argument that the overall signifier for the overall organism is the ant colony not the individual ants in a similar way our individual cells have no identity other than as part of the larger organism-cancer cells may be disagreeing ;)

Given the self assembler aspect I think there is an argument that it is as much a signifier of identity for the individual organism as multicellularity or whatever role that organism takes in its more developed stage.

Self assembly has basically been ignored as we are more used to looking from the completed animal rather than from the point of view of the initiator assembler and we don’t tend to think in terms of self assembly/organisation anyway.

If we were to look at a man made self assembler I would rather think people will automatically designate all the stages of the development as that particular type of self assembler machine, rather than just any half completed or fully completed ones. If we do for them it calls into question some current thinking on biological classification of zygotes etc.

What do you think?


Cheers
Simon


Answer
Dear Simon,

Interesting ideas, and certainly more in the realm of philosophy, at this point, than science, which makes it even more interesting in many ways.  But like many philosohical questions, yours may not have a definitive answer.  But we can talk about it and have fun.  :)

When one comes down to it, classification and naming are, to some extent, arbitrary.  Even in the scientific community there is some disagreement about what constitutes a Living Thing or Not a Living Thing, and how to classify things that are "borderline".  We all can agree on what things *are*, functionally, but we cannot always agree on how to classify (and name) them.

When you write of the imaginary, self-assembling robot, you are essentially creating a mechanical version of a living thing.  But can it be considered the same as a living thing?  A living thing is more than the sum of its parts.  There is a synergy among its parts that results in something different from any machine now known.  

If such a machine did exist--one that had all the properties we now use to define life--then I'm sure humans would spend endless time arguing about how to classify it. (As I'm sure you know, this subject has already been tackled by more than a few science fiction authors.)

I'm clueless about how robots and machines are classified.  But biologists usually use a fairly strict definition for what constitutes a living thing.  To be considered truly alive, a thing must:

1.  Be able to reproduce itself (without help from a different type of organism) *and*

2.  Have an organized physical structure (anatomy) *and*

3.  Have chemical reactions that allow it to function (metabolism) *and*

4.  Be able to decrease internal entropy by utilizing the energy in matter or free energy. *and*

5.  Have the ability to maintain (to a greater or lesser degree) a constant internal environment (homeostasis) *and*

6.  Be able to react to internal and external stimuli *and*

7.  Evolve in response to environmental pressures (a populational phenomonenon; not an individual one)

If any one of these properties is lacking, the thing is not considered truly alive.  (Okay, not everyone agrees even on this, though *most* do...)

By this definition, the robot you describe would not be considered truly alive, and so possibly not subject to the same classification schemes we use for living things.  

If you want to imagine a machine that has all the aforementioned properties of life, then it would be as difficult to classify--at all its developmental stages--as a living thing is at all its developmental stages.  Since it's imaginary, so its classification and treatment must remain moot.  And we're back to Square One.  

When you say:  "...if we take what it requires to currently create a clone from the nucleus of a skin cell and an empty egg you have effectively destroyed the original skin cell and have just inserted the blueprint in the potential initiator shell.  The skin cell didn’t have potential it was rather the plans in the nucleus."

Well...sort of.  It's actually being done the other way around:  the nucleus from a skin cell is taken and inserted into an ablated (nucleus destroyed) ovum.  The reason for this is because an ovum has transcription factors laid down in the cytoplasm (by the mother/organism that made the ovum) that set developmental gears in motion.  These factors no longer exist in the progeny cells of the original zygote, having been used up early in development.  

So it's actually the *skin cell*, not the ovum, that has the potential for development into a whole organism (with a little help from the cloners); it just needs that genetic nudge from the cytoplasmic elements in the ovum.  But I think we both agree that simple genetic potential doesn't define the object as an individual.

When you say:  "If we were to look at a man-made self assembler I would rather think people will automatically designate all the stages of the development as that particular type of self assembler machine, rather than just any half completed or fully completed ones."

...I'm not at all sure this would be the case.  If the machine were really that similar in development to a living organism, I think people would have just as much trouble classifying it.  And they would argue about it, too.  :)

For my own interest, when you say, "If we do for them it calls into question some current thinking on biological classification of zygotes etc."

...are you aware of any biological classification of zygotes?  I've actually not heard of anyone even discussing whether a zygote is an individual organism or not--with the notable exception of Homo sapiens zygotes when it come to arguments about abortion rights.

But no other species I know of is considered an individual organism at the zygote stage, which makes me wonder why Homo sapiens should be considered any different from them.  We differ from other species only in degree, and not in kind.

What do you think?  :)

Dana