Abstract
Nervous systems are composed of populations of cells that are synaptically connected in a highly predictable manner, and we have called two interconnected populations a pair of matching populations. Heritable genetic changes that affect a pair of matching populations can be evolutionary only when this matching quality is not disrupted. We distinguish two types of heritable change. Concordant heritable changes autonomously preserve the match and are thus automatically candidates for what we call type I evolutionary change. Nonconcordant heritable changes, on the other hand, are those that do not autonomously preserve the match. Those nonconcordant heritable changes that can use other normally present ontogenetic mechanisms to preserve the match are candidates for what we call type II evolutionary change. One example of such an ontogenetic mechanism consists of the production of excess neuroblasts and the subsequent weeding out (via cell death) of those that do not successfully match. Because normal ontogeny is an integral part of type II evolutionary change, ontogenetic manipulations can give evolutionary insights. Embryonic graft experiments, in particular, can elucidate the nature of ontogenetic mechanisms that participate in type II changes. Thus, some developmental experiments can be considered to be evolutionary experiments.
Keywords: cell death, evolution experiments, excess cells, matching populations, neural ontogeny
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Selected References
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- Alley K. E. Morphogenesis of the trigeminal mesencephalic nucleus in the hamster: cytogenesis and neurone death. J Embryol Exp Morphol. 1974 Jan;31(1):99–121. [PubMed] [Google Scholar]
- Clarke P. G., Cowan W. M. The development of the isthmo-optic tract in the chick, with special reference to the occurrence and correction of developmental errors in the location and connections of isthmo-optic neurons. J Comp Neurol. 1976 May 15;167(2):143–164. doi: 10.1002/cne.901670203. [DOI] [PubMed] [Google Scholar]
- Cowan W. M., Wenger E. Cell loss in the trochlear nucleus of the chick during normal development and after radical extirpation of the optic vesicle. J Exp Zool. 1967 Mar;164(2):267–280. doi: 10.1002/jez.1401640210. [DOI] [PubMed] [Google Scholar]
- Hamburger V. Cell death in the development of the lateral motor column of the chick embryo. J Comp Neurol. 1975 Apr 15;160(4):535–546. doi: 10.1002/cne.901600408. [DOI] [PubMed] [Google Scholar]
- Hollyday M., Hamburger V. Reduction of the naturally occurring motor neuron loss by enlargement of the periphery. J Comp Neurol. 1976 Dec 1;170(3):311–320. doi: 10.1002/cne.901700304. [DOI] [PubMed] [Google Scholar]
- Landmesser L., Pilar G. Synaptic transmission and cell death during normal ganglionic development. J Physiol. 1974 Sep;241(3):737–749. doi: 10.1113/jphysiol.1974.sp010681. [DOI] [PMC free article] [PubMed] [Google Scholar]
- PRESTIGE M. C. CELL TURNOVER IN THE SPINAL GANGLIA OF XENOPUS LAEVIS TADPOLES. J Embryol Exp Morphol. 1965 Feb;13:63–72. [PubMed] [Google Scholar]
- Pollack E. D. Normal development of the lateral motor column in the brachial cord in Rana pipiens. Anat Rec. 1969 Jan;163(1):111–119. doi: 10.1002/ar.1091630113. [DOI] [PubMed] [Google Scholar]
- Rogers L. A., Cowan W. M. The development of the mesencephalic nucleus of the trigeminal nerve in the chick. J Comp Neurol. 1973 Feb 1;147(3):291–320. doi: 10.1002/cne.901470302. [DOI] [PubMed] [Google Scholar]
- Rubel E. W., Smith D. J., Miller L. C. Organization and development of brain stem auditory nuclei of the chicken: ontogeny of n. magnocellularis and n. laminaris. J Comp Neurol. 1976 Apr 15;166(4):469–489. doi: 10.1002/cne.901660408. [DOI] [PubMed] [Google Scholar]
- SINGER M. The influence of the nerve in regeneration of the amphibian extremity. Q Rev Biol. 1952 Jun;27(2):169–200. doi: 10.1086/398873. [DOI] [PubMed] [Google Scholar]
- Sohal G. S. An experimental study of cell death in the developing trochlear nucleus. Exp Neurol. 1976 Jun;51(3):684–698. doi: 10.1016/0014-4886(76)90191-6. [DOI] [PubMed] [Google Scholar]
- Sohal G. S., Holt R. K. Cell death during normal development of the abducens nucleus. Exp Neurol. 1977 Mar;54(3):533–545. doi: 10.1016/0014-4886(77)90255-2. [DOI] [PubMed] [Google Scholar]