Towards the end of that piece "On Where Life Begins" , will post what is in-play towards the end on the Neurological data and possible interpretations . But not a subject that will ever yet be treated to anyone's fulfillment based completetly on pure science alone .
Its not yet a perfected world , with perfected human beings living in it , I don't pretend that the ideas expressed below are all encompassing ...but will express some of science's findings, and address somewhat your/our questions.
Here deals with
" The contemporary idea of the acquisition of humanness is based on the contemporary theories of developmental embryology. "
Neurological view
...Where Life Begins :
devbio.com
Although most cultures identify the qualities of humanity as different from other living organisms, there is also a universal view that all forms of life on earth are finite. Implicit in the later view is the reality that all life has both a beginning and an end, usually identified as some form of death. The debate surrounding the exact moment marking the beginning of a human life contrasts the certainty and consistency with which the instant of death is described. Contemporary American (and Japanese) society defines death as the loss of the pattern produced by a cerebral electroencephalogram (EEG). If life and death are based upon the same standard of measurement, then the beginning of human life should be recognized as the time when a fetus acquires a recognizable EEG pattern. This acquisition occurs approximately 24- 27 weeks after the conception of the fetus and is the basis for the neurological view of the beginning of human life.
These principles of the neurological view of the beginning of human life are presented in The Facts of Life, a book written by Harold Morowitz and James Trefil in 1992 concerning the abortion controversy. An electroencephalogram (EEG) is a simple medical procedure in which electrodes are attached to different locations on a patient's head and the voltage difference over time is measured between the two points. The voltage data is plotted against time to produce "brain waves" with up and down voltage oscillations that are representative of the organized electrical activity of the brain (Morowitz and Trefil 1992). Medical professionals use a patient's EEG pattern to identify a broad spectrum of mental states. Although EEGs are often used as a diagnostic tool, the exact mechanism behind how an EEG pattern is linked to an individual's cerebral neuron activity remains a mystery (Morowitz and Trefil 1992).
Despite lacking a precise explanation for the connection between the EEG and neural activity, there is a strong argument that the unique and highly recognizable EEG pattern produced by a mature brain is a defining characteristic of humanity (Morowitz and Trefil 1992). Therefore, the moment that a developing fetus first exhibits an EEG pattern consistent with that of a mature brain is indicative of the beginning of human life. It is from this point and onward during development that the fetus is capable of the type of mental activity associated with humanity (Morowitz and Trefil 1992).
Because the state of modern technology still prohibits EEGs in utero, brain activity data for humans at various stages of development has been gathered using premature infants. Observations to date have led to the conclusion that 25 weeks of gestation is required for the formation of synapses needed for recognizable neural activity. At this point in development, the recognizable signals exist only as intermittent bursts that interrupt periods of random activity (Morowitz and Trefil 1992). This conclusion is summarized by Donald Scott who in his book Understanding the EEG wrote, "Attempts have been made to record cerebral activity of premature infants and they have succeeded (only) if the gestational age was 25 weeks or more (Morowitz and Trefil 1992)." Such claims, as well as arguments that endorse an opposite argument, are for many the foundation for any dispute over defining the inception of human life. Consequently, the principles of the neurological view are tenets in the debate over another controversial subject: abortion.
Champions for a fetus's right to life often claim that the brain of a human fetus begins to show electrical activity at a remarkably early age. A key moment in the history of the abortion debate is the production and release of "The Silent Scream," an influential abortion film that graphically depicts the fetal response to its termination. The video accompanies the abortion of a 12-week-old fetus with the words "Now this little person at twelve weeks is a fully formed absolutely identifiable human being. He has had brain waves for at least six weeks..." (Morowitz and Trefil 1992). Although such arguments appeal to both the emotion by depicting an infant, though still developing, in a moment of pain and crisis and the intellect by presenting a scientific line of reasoning, the position presented by the film conflicts widely accepted developmental theory. For instance, the film contends that a fetus has brain waves after 12 weeks and suggest, even in the title "The Silent Scream," that it reacts to its termination with fear and pain. These contentions contradict scientific evidence that indicates neural connections in the cerebral cortex have yet to develop in a 12-week-old fetus. Lacking these basic neural networks, the developing fetus is incapable of feeling the emotions recognized as fear or pain (Morowitz and Trefil 1992). The film's position is further contrasted by evidence that suggests a 12-week-old fetus is not yet capable to take direct actions in response to a thought. The developing fetus is therefore incapable of recognizing potential danger and unable to either be fearful of it or actively evade it through movement or any other willful activity (Morowitz and Trefil 1992).
(For information concerning how photographs of the embryo are often misrepresented on anti-abortion literature and websites, see Images of Embryos Used by Anti-Abortion Activists.)
In addition to presenting 25 weeks as a critical developmental landmark, other proponents of the neurological view believe that events of the eighth week of human gestation represent the key moments marking the beginning of human life. Contemporary philosophical arguments for designating week 8 as the beginning of human life proceed in accordance with the following format: humanness requires rational thought and rational thought requires a brain and a nervous system. Philosophers who present such arguments contest that an embryo is not a human being until it has a rudimentary nervous system. At week 8, the embryo has completed organogenesis, meaning it has simple, undeveloped versions of all the basic organ systems, including the nervous system (Shannon and Wolter 1990) Philosophers who subscribe to this perspective pay close attention to the progressively increasing complexity of the nervous system or the first weeks and months of pregnancy. At week 5 the first neurons begin to appear, at week 6 "the first synapses ... can be recognized," and at 7.5 weeks the embryo displays its first reflexes in response to stimulus. (Shannon and Wolter 1990). Thus around week 8 the embryo has a basic three-neuron circuit, the foundation of a nervous system necessary for rational thought. (Shannon and Wolter 1990).
It should come as no surprise that this contemporary philosophical debate also consists of a second argument, which is in direct opposition to the aforementioned position. There are philosophers who believe that the capacity for rational thought is indeed a prerequisite of humanness, but that an 8-week-old embryo does not have the capacity for rational thought. At 8 weeks an embryo displays reflexes that are the result of its budding nervous system, but it does not yet have the structures necessary to engage in true rational activity in contrast to mere reflex motivated movement. (Shannon and Wolter, 1990)
A third developmental landmark presented by proponents of the neurological view occurs at 20 weeks. Some advocates of the philosophy that a prerequisite for humanness is the capacity for rational thought believe that the existence of a primitive nervous system after 8 weeks, with the ability to respond by reflex to stimulation, does not amount to rational thought. The embryological landmark of 20 weeks marks the completion of the development of the thalamus, a region of the brain, which enables the integration of the nervous system. Philosophers who support this view therefore believe that only after 20 weeks of gestation can the embryo be said to have the capacity for rational thought.
The precept at the heart of the neurological view of the beginning of human life is the significant development of neural pathways that are critical for characteristic human brain activity. The formation of these neural connections is often viewed to culminate in the acquisition of humanness, a stage during the third trimester of human gestation when the overwhelming majority of neural pathways in the cerebral cortex are established (Morowitz and Trefil 1992). The contemporary concept of the acquisition of humanness was developed and elaborated during the later half of the twentieth century by theological and biological leaders who emphasized the importance of the cerebral cortex in characterizing humanness. The Jesuit scholar and anthropologist scientist Pierre Teilhard de Chardin presented his belief that the transcendence of humanity was dependant upon the successful maturation of the cerebral cortex. Bernard Haring, a permanent Catholic theologian of the 1970s argued that individuality and the uniqueness of personal characteristics and activities originated from the cerebral cortex. A decade later, the anatomist Paul Glees argued "the (cerebral cortex) represents the signature of a genetically unique person" (Morowitz and Trefil 1992)
The contemporary idea of the acquisition of humanness is based on the contemporary theories of developmental embryology. Cerebral nerve cells accumulate in number and continually differentiate through the end of the second trimester of human pregnancy (Morowitz and Trefil 1992). However, it is not until the seventh month of gestation that a significant number of connections between the newly amassed neurons begin to take form. It is only after the neurons are linked via synapse connections that the fetus is thought to acquire humanness. Just as a pile of unconnected microchips is incapable of functioning and is therefore not called a computer, the unconnected neurons of the pre 24-week fetal brain lack the capacity to function, thus the developing fetus has yet to acquire humanness (Morowitz and Trefil 1992). |
