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Re: Are We Still Evolving?
Osmo Ronkanen (ronkanen@cc.Helsinki.FI)
20 Nov 1995 22:17:05 +0200
In article <47tqom$8j4@nntp.ucs.ubc.ca>, pete <VINCENT@REG.TRIUMF.CA> wrote:
>Julian Treadwell (jay@iprolink.co.nz) sez:
>`banerkx@news.infi.net (Kaushik Banerjee) wrote:
>`>Are we still evolving? Since we put stress on our
>`>environment, rather than vice versa, are we still evolving?
>`>
>`Because of genetic phenomena such as genetic drift, recombination and
>`mutation, evolution is not a process which could ever actually stop. And
>`of course breeding selection hasn't stopped either, even if it's no
>`longer so much due to 'natural' pressures.
>
>What breeding selection there still exists must be fairly minimal.
>Someone here claimed that they had a figure that 34% of affluent
>white females (I think that was in the us) didn't get around to
>breeding, but in my experience, just about every person who survives
>to adulthood, and is physically capable, or can be made so by
>medical intervention, except the very few who chose monastic life, and
>a subset of the homosexual population, manages to breed. And few of
>them have more than three children, regardless of how desirable
>they are. Thus in the general population I see almost no
>differential reproduction. As far as the 34% figure mentioned above,
>I'd want to see the research. I simply don't believe it.
>
Here are birth rates for first child in 1993. One can get the figure
how many percent of women have children by adding them up and
multiplying by 5 and dividing by 1000.
All White Black
10-14 1.3 0.8 4.4
15-19 45.3 40.6 74.2
20-24 52.9 53.1 55.6
25-29 42.5 44.4 28.3
30-34 21.7 22.4 13.5
35-39 7.1 7.3 4.4
40-44 1.2 1.2 0.8
45-49 0.1 0.1 0.0
86.1% 85.0% 90.6%
One should realize that this is a periodic figure (just like the total
fertility rate) and as such it can in any given year show figures that
are off the actual figure (If the trend is that women have first children
later than before, the figure is too low and if the trend is the opposite
the figure is too high).
What one calculates is actually total fertility rate for first children
and as no woman can have their first child twice one also gets the
percentage of women who have their first child and which is same as the
percentage of women who have children.
Source: Advance Report of Final Natality Statistics, 1993
Stephanie J. Ventura, A.M.; Joyce A. Martin, M.P.H.; Selma M. Taffel; T.
J. Mathews, M.S.; and Sally C. Clarke, Division of Vital Statistics
Vol. 44, No. 3 Supplement + September 21, 1995
Final Data From the CENTERS FOR DISEASE CONTROL AND PREVENTION/National
Center for Health Statistics.
Osmo
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