Week 3: Human Genetic Evolution

This was a lot to digest and many different viewpoints and theories were discussed …. here are my pithy takeaways.

Origins of Populations: 

Summary: By analyzing the variations at many loci, phylogenetic trees can be constructed that relate the many populations of the world. 

Comment:  Science proves we are all related.

 

DNA Studies:

Summary: Genetic studies can tell us how human migration occurred – when we appeared, what we were like, and where we went.

Comment: These are theories, and should be understood in that context

 

Discovery of Early Hominids:

Summary: We’re not sure if the immediate ancestors of humans were members of the genus Australopithecus.  More hominid fossils from 3-4 million years ago need to be discovered to determine the place of Kenyanthropus (the “flat-faced man of Kenya”) or Lucy in our evolution. 

Comment:  But will we ever really know?  We can guess, but every time new evidence is found, the theory will change.

 

Early Transitional Humans

Summary: We are not the only species of humans who have ever lived

Comment:  How are species classified as “Homo?”

 

Early Archaic Homo sapiens and Their Contemporaries

Summary: Evolution of species varied from region to region and cranial capacity is larger in more recent species

Comment:  I am curious what cranial capacity is a measure of.  Could the increased development in this area, necessitated a deficiency in another area?

 

Early Modern Homo sapiens:

Summary: Homo Sapiens and Neandertals were their contemporaries.  Since the 1980’s there have been 2 conflicting arguments about the evolution of Homo Sapiens:  Replacement Model Arguments and Regional Continuity Model.

Comment:  The replacement model says that the regional anatomical differences that we see among humans today are recent developments.  This is difficult for me to believe that a species existed with limited anatomical difference.


Homo Ergaster:

Summary: H. ergaster is more closely related to archaic and modern Homo sapien than Homo erectus form Asian.

 

Early Models of Evolution

Summary:  Discussed different culture’s creation stories and thoughts from a range of philosophers and scientists

Comment:  There are lots of theories, stories and models of evolution.  

 I think all of these are valid and speak to the culturally relevant needs of different groups.  I liked the emphasis on this article about creation stories from different cultures, and the different stories of life forms being created out of primordial substance(s).

 

Origins of Life

Summary:  Another theory on how life started.  Alexander Ivanovich Oparin theorized that the first atmosphere was made largely of water vapor (H2O), carbon dioxide (CO2), carbon monoxide (CO), nitrogen (N2), methane (CH4, and ammonia (NH3. As the surface of Earth cooled again, torrential rains of this mixture formed the first seas, the “primordial soup.”

Comment:  All these readings make me think, “everything is just a theory.”

 

Nasa Scientists Find Clues That Life Began in Deep Space

Summary:  Some scientists believe that the delivery – by comets, meteorites and interplanetary dust – of similar organic compounds born in interstellar space might have “kick-started” life on Earth.

Comment:  Another theory, all plausible

 

Early evolution of life on Earth

Summary:  Some scientists believe that the delivery – by comets, meteorites and interplanetary dust – of similar organic compounds born in interstellar space might have “kick-started” life on Earth.

Comment:  More theory on the evolution of life.  I appreciated the comment about lack of evidence in this article and the questions raised.  One thing I thought was interesting is that  the early geological evolution of the Earth and the early evolution of life occurred in parallel.

 

Natural Selection and Speciation

Summary & Comments: I thought the example used to show that a common understanding that if organisms are separated for long enough, they will to develop into separate species was interesting.  The example was of HeLa cells which are a widely-cultured research “organism” available through a number of biological supply companies that originally came from a woman with cervical cancer. The question is being asked, are these cells still “human?” While HeLa cells currently being grown in tissue culture are descendents of the original human cancer cells, by now they have mutated so much that it’s questionable whether they can still be considered “human” tissue.

 

How did the first cells evolve?

Summary: 2 theories discussed:  1) UV, Lightning, heat caused hydrocarbons to be formed in the early atmosphere of the earth. And 2) life began around thermal vents caused by volcanic activity on the ocean floor.

Comments:  I think this was one of the most lay-person friendly articles that was very simple in its explaination …..or, maybe because I read this first thing in the morning, versus at night like the other articles, it was easier to read.

 

Spontaneous Generation

Summary:   This article discusses the theory of spontaneous generation, that ome life forms arise spontaneously from non-living matter. It gives the examples of the experiments that led up to the final conclusions, that “spontaneous generation” is caused by the existence of microorganisms are everywhere – even in the air.

Comment:  The article was logical and makes sense, and yes …. Out there in the world, microorganisms abound and are creating all sorts of life forms.

 

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