Summary of ‘Saltation and Stasis: A Model of Human Growth (Lampl, M. Veldhuis, J.D. and Johnson, M.L. 1992)’
The current concepts regarding the biology of human growth are primarily based on the data collected on height and weight in auxological studies. The individuals have been measured traditionally during infancy at quarterly intervals and annually or biannually during their childhood or adolescence. The growth in human is viewed as a continuous process characterised by the changing velocity with age.
The study aims to understand the trends and availability of human growth hormone and the resulting clinical potential for treatment of growth disorders, along with the advances in molecular biology describing the normal cellular growth control mechanisms, underscore the importance of clarifying normal growth dynamics.
- Time-Intensive Data and an Analytic Descriptor
The serial length measurements of the normal infants that were assessed in this study were assessed weekly [n=10], semi-weekly [n=18] and daily [n=3]. Out of which 19 infants were females and 12 were males and they were assessed during their first 21 months. The study was conducted after the parental informed consent.
There were thirty one clinically normal Caucasian American infants that were assessed during the study which were between the ages of 3 days to 21 months.
In order to conduct this research, recumbent length, weight and head circumference were measured as per the standard techniques. The measurements of the serial length were the focus of the report and the total recumbent length was measured to the nearest 0.05 cm by two observers with a specifically designed infant measuring board which was used during home visits.
As per the data showed the growth in length occurred by discontinuous, apperiodic salutatory spurts which were 0.5 to 2.5 cm in amplitude during intervals that were separated by no measureable growth.
According to the data it is suggested that 90 to 95 percent of the normal development during infancy is growth-free and length accretion is a distinctly saltatory process of incremental bursts punctuating conditions stasis.
- Saltation and Stasis
Each new generation, it seems, produce few young paleontologists eager to document examples of evolutionary change in their fossils. The changes we have always sought, naturally, were the kind of gradual, progressive. Most of the time their efforts have gone unrewarded – their fossils, rather than exhibiting the expected pattern, seem simply continue virtually unchanged. This extraordinary conservatism seemed, eager to find paleontologist evolutionary change, as if there had been evolution (Cohen, and Haas 1999). Thus, studies documenting the persistence conservative rather than gradual evolutionary change were considered a failure, and most of the frequencies were not even published. Most paleontologists were aware of stability, the absence of change we call stasis. But with respect to the same evolution, paleontologist’s stasis usually regarded as “negative” rather than as a contradiction of the prediction of gradual change, progressive evolutionary. And (until today) will continue to invoke the discontinuities in the fossil record as the main reason they are so few cases of gradual change (SAS 1989).
Gould (Tufts, Haas, Beard and Spielvogel 1985) wrote in the same sense that “When Niles Eldredge and I proposed the theory of punctuated equilibrium in evolution did to grant stasis phylogenetic lineages in the position of” noteworthy “-because stasis had been previously ignored as no proof of evolution, but all paleontologists knew their relative high frequency.” What Gould and Eldredge had to avoid, however, was what Eldredge (Heinrichs, Munson, Counts, Cutler and Baron 1995) described as “not unreasonable junking the fringe of lunatics who have suffered in the past some paleontologists as they also realized the differences between evolutionary theory contemporary, on the one hand, and patterns of change in the fossil record by the other. ” In short, they had to avoid appearing as embracing saltationism.
Saltationism extended to the extreme proposition to propose that the first bird must have come out of a reptile egg. George Gaylord Simpson wrote a critical review of the book by Schindewolf (Boas 1892), but conceded that the eccentric author’s conclusions were based on a thorough knowledge of the fossil evidence. The problem was that there Schindewolf tried to impose an interpretation of the fossil evidence that could be accepted by geneticists, or perhaps relied too much on the approval of the geneticist Richard Goldschmidt. Simply, launched and published what they called fossils, and fossils said “saltation.” A research conducted by Titterington, Smith and Makov (1985) concluded that during recanalization of growth pattern RNPTMBPN is predominantly saltatory growth and the presence of stasis was associated with decreased caloric intake. The normal growth saltation is wrong and stasis patterns that have not been documented State recanalization during growth in VLBW infants.
Paleontologists who have to work under the influence of neo-Darwinism do not have the same freedom to draw those conclusions the evidence leads them (Klein, Munson, Bacher, Cutler and Baron 1994). Eldredge candidly described the dilemma of paleontologist as either you cling to the conventional theory despite how badly fossils conform to it, or you focus on empirical evidence and say that the jumps seem a reasonable model of the process evolution-in which case you have to embrace a set of propositions biological questionable (Johnson, Veldhuis and Lampl 1996). Paleontology, it seems, is a discipline that is sometimes inappropriate ‘focus on empirical evidence. Moreover, one cannot simply lie ahead and fabricate evidence of Darwinian evolution, and Eldredge wrote poignantly about how this combination of restrictions makes it difficult to progress professionally (Dearborn and Rothney 1941).
What complicates the normal routine is the mess for a PhD. A doctoral thesis research is actually learning, and the dissertation is a comprehensive report showing the candidate’s ability to develop and successfully pursue original scientific research. Sounds reasonable, but it is huge pressure to get results, and positive results. In these grim circumstances, paleontologists clearly needed a theory that would allow them to report on their projects as successful, but they were limited to working within the neo-Darwinian synthesis (Johnson, Veldhuis and Lampl 1996). What was needed was a theory saltationism enough to allow paleontologists post but gradual enough to placate the Darwinists. Punctuated equilibrium statesman achieves this feat of making the change process inherently invisible. One can imagine those forms isolated peripheral changing so much and so fast as you want, because no one will ever see. Gould and Eldredge have invariably described as a punctuated equilibrium Darwinian Theory, not as a repudiation of Darwinism saltation. Moreover, it is easy to see how some people got the impression that it was at least suggesting the saltationism, if he was not being openly proposed (Hermanussen and Geiger-Benoit 1995).
- The problem with saltationism, however, is that when examined closely it be just a meaningless middle ground between evolution and special creation. In the words of Richard Dawkins, the biblical creation of man from the dust of the earth could call a jump. In terms of fossil evidence, the jump only means that a new form appeared from nowhere, and we have no idea how (Klein, Munson, Bacher, Cutler and Baron 1994). As a scientific theory, “evolution by leaps” is precisely what Darwin called the principle: garbage. Gould and Eldredge understand this, and so, despite insinuations saltationism (especially by Gould), have always kept their lines of retreat open to orthodox Darwinian gradualism. This leads to the most basic question of all. If there are so many problems with Darwinism and if no satisfactory alternative within the evolutionary framework, why not re-evaluate the frame? What makes our scientists are so absolutely sure that everything actually evolved from a simple beginning (Dearborn and Rothney 1941)?
However the saltation and stasis better describe the data as compared to any other model of continuous daily growth or a pattern of small and continuous growth spurts. Thus the mathematical models are useful for investigation particularly for comparing alternative hypotheses about nature of the process. But the saltation and stasis model is found to better fit the experimental data than the slowly varying smooth continuous functions (Hermanussen and Geiger-Benoit 1995).
Boas, F., 1892, The growth of children. Science, 19, 256-257, 281-282.
Dearborn, W. R., and Rothney, J. W. M., 1941, Predicting the Child’s Development (Cambridge: SciArt Publishers).
Cohen, J. H., and Haas, J. D., 1999, The comparison of mixed distribution analysis with a three-criteria model as a method for estimating the prevalence of iron de®ciency anemia in Costa Rican children aged 12-23 months. International Journal of Epidemiology, 28, 82-89.
Heinrichs, C., Munson, P. J., Counts, D. R., Cutler Jr, G. B., and Baron, J., 1995, Patterns of human growth. Technical comment. Science, 268, 442-444.
Hermanussen, M., and Geiger-Benoit, K., 1995, No evidence for saltation in human growth. Annals of Human Biology, 22, 341-345.
Johnson, M. L., Veldhuis, J. D., and Lampl, M., 1996, Is growth saltatory? The usefulness and limitations of frequency distributions in analyzing pulsatile data. Endocrinology, 137, 5197-5204.
Klein, K. O., Munson, P. J., Bacher, J. D., Cutler, Jr, G. B., and Baron, J., 1994, Linear growth in the rabbit is continuous, not saltatory. Endocrinology, 134, 1317-1329.
Lampl, M. Veldhuis, J.D. and Johnson, M.L., 1992, Saltation and Stasis: A Model of Human Growth, Journal of Science, 28, 801-803
SAS, 1989, SAS/STAT User’s Guide Version 6, 4th edn, vol. 2 (Cary, NC: SAS Institute Inc).
Titterington , D. M., Smith, A. F. M., and Makov, U. E., 1985, Statistical Analysis of Finite Mixture Distributions (Chichester: John Wiley & Sons).
Tufts, D. A., Haas, J. D., Beard, J. L., and Spielvogel, H., 1985, Distribution of hemoglobin and functional consequences of anemia in adult males at high altitude. American Journal of Clinical Nutrition, 42, 1-11.