Robert Kar
Sat, Jan-20-07, 06:16
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Going Under Down Under: Early people at fault in Australian
extinctions Sid Perkins
A lengthy, newly compiled fossil record of Australian
mammals bolsters = the notion that humanity's arrival on the
island continent led to the = extinction of many large
creatures there.=20
Archaeological evidence suggests that people arrived in
northern and = western Australia about 50,000 years ago (SN:
3/15/03, p. 173: Available = to subscribers at =
http://www.sciencenews.org/articles/20030315/note10.asp). By
5,000 years = later, about 90 percent of the continent's
mammals larger than a house = cat had gone extinct, says Gavin
J. Prideaux, a paleontologist at the = Western Australian
Museum in Perth. Casualties of that era include = several
species of kangaroos and wombats as well as marsupials that =
filled the ecological niches elsewhere populated by lions,
hyenas, = hippos, and tapirs.=20
By unearthing and cataloging specimens from a group of
fossil-rich caves = about 300 kilometers southeast of
Adelaide, Prideaux and his colleagues = assembled a nearly
complete record of the past 500,000 years. Most of = the 62
species of nonflying mammals on the list fell into the caverns
= via sinkholes, but some remains were brought in by owls that
roosted = there.=20
Scientists had compiled a long-term climate record for
southeastern = Australia by analyzing the caves' stalactites.
Those structures formed = and grew when rainfall was plentiful
but not during dry spells.=20
During most of the past 500,000 years, the number and
diversity of = mammal fossils found in the Australian caves
decreased only during = intervals when the local climate was
dry. When moisture returned, so did = the animals. The only
exception is the die-off of mammals between 50,000 = and
45,000 years ago, the team reports in the January Geology.=20
Those extinctions occurred at least 25,000 years before the
most recent = ice age began. "The climate was stable then, and
mammals really = shouldn't have been going extinct," says
coauthor Richard G. Roberts, a = geochemist at the University
of Wollongong in Australia. "The only thing = that's new
during that period is people," he adds.=20
Scientists are debating how people might have caused the
extinctions. = Some researchers argue that the new inhabitants
drastically altered = Australian ecosystems by burning the
landscape (SN: 7/23/05, p. 61: = Available to subscribers at =
http://www.sciencenews.org/articles/20050723/note11.asp).
However, large = species may have died off gradually when
people preyed on the mammals' = offspring faster than the
animals reproduced, says Roberts.=20
The fossil record compiled by Prideaux and his colleagues
shows that = "the mammal fauna was resilient through time,
despite climate = fluctuations," says David W. Steadman, a
paleontologist at the = University of Florida in Gainesville.
Changes in mammal populations = during times of climate change
"were nothing like those that occurred = after people showed
up," he notes.=20
"To think climate caused these extinctions is [now]
untenable," comments = Gifford H. Miller, a geologist at the
University of Colorado at Boulder. =
--------------------------------------------------------------
------------=
-------
If you have a comment on this article that you would
like = considered for publication in Science News, send
it to = editors@sciencenews.org. Please include your
name and location. =20
Source: ScienceNews
http://www.sciencenews.org/articles/20070120/fob6.asp
Posted by Robert Karl Stonjek
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<DIV>
<DIW>
<DIW1>Going Under Down Under: Early people at fault in
Australian = extinctions</H3>
<DIX><STRONG>Sid Perkins</STRONG></P>
<DIY>A lengthy, newly compiled fossil record of Australian
mammals = bolsters the=20 notion that humanity's arrival
on the island continent led to the = extinction of=20
many large creatures there.=20
<DIZ>Archaeological evidence suggests that people arrived in
northern and = western=20 Australia about 50,000 years
ago (SN: 3/15/03, p. 173: Available to = subscribers=20
at <A=20 href=3D"http://www.sciencenews.org/articles/200-
30315/note10.asp">http://w=
ww.sciencenews.org/articles/20030315/note10.asp</A>).=20
By 5,000 years later, about 90 percent of the continent's
mammals larger = than a=20 house cat had gone extinct,
says Gavin J. Prideaux, a paleontologist at = the=20
Western Australian Museum in Perth. Casualties of that
era include = several=20 species of kangaroos and wombats
as well as marsupials that filled the=20 ecological
niches elsewhere populated by lions, hyenas, hippos, and
= tapirs.=20
<DIZ>By unearthing and cataloging specimens from a group of
fossil-rich = caves=20 about 300 kilometers southeast of
Adelaide, Prideaux and his colleagues=20 assembled a
nearly complete record of the past 500,000 years. Most of
= the 62=20 species of nonflying mammals on the list fell
into the caverns via = sinkholes,=20 but some remains
were brought in by owls that roosted there.=20
<DIZ>Scientists had compiled a long-term climate record for
southeastern = Australia=20 by analyzing the caves'
stalactites. Those structures formed and grew = when=20
rainfall was plentiful but not during dry spells.=20
<DIZ>During most of the past 500,000 years, the number and
diversity of = mammal=20 fossils found in the Australian
caves decreased only during intervals = when the=20 local
climate was dry. When moisture returned, so did the
animals. The = only=20 exception is the die-off of
mammals between 50,000 and 45,000 years ago, = the=20
team reports in the January <I>Geology</I>.=20
<DIZ>Those extinctions occurred at least 25,000 years before
the most = recent ice=20 age began. "The climate was
stable then, and mammals really shouldn't = have been=20
going extinct," says coauthor Richard G. Roberts, a
geochemist at the = University=20 of Wollongong in
Australia. "The only thing that's new during that =
period is=20 people," he adds.=20
<DIZ>Scientists are debating how people might have caused the
extinctions. = Some=20 researchers argue that the new
inhabitants drastically altered = Australian=20
ecosystems by burning the landscape (SN: 7/23/05, p. 61:
Available to=20 subscribers at <A=20 href=3D"http://www.-
sciencenews.org/articles/20050723/note11.asp">http://w=
ww.sciencenews.org/articles/20050723/note11.asp</A>).=20
However, large species may have died off gradually when
people preyed on = the=20 mammals' offspring faster than
the animals reproduced, says Roberts.=20
<DIZ>The fossil record compiled by Prideaux and his colleagues
shows that = "the=20 mammal fauna was resilient through
time, despite climate fluctuations," = says=20 David W.
Steadman, a paleontologist at the University of Florida
in = Gainesville.=20 Changes in mammal populations during
times of climate change "were = nothing like=20 those
that occurred after people showed up," he notes.=20
<DIZ>"To think climate caused these extinctions is [now]
untenable," = comments=20 Gifford H. Miller, a geologist
at the University of Colorado at Boulder. =
<DIZ></P> <HR width=3D"75%">
<DIV align=3Dcenter> <TABLE cellSpacing=3D0 cellPadding=3D0
width=3D430 border=3D0> <TBODY> <TR> <TD><FONT face=3DArial
size=3D2>If you have a comment on this = article that you=20
would like considered for publication in <I>Science News</I>,
send = it to=20 <A = href=3D"mailto:editors@sciencenews.org">-
editors@sciencenews.org</A>.=20 Please include your name and
location.</FONT>=20 </TD></TR></TBODY></TABLE></DIV></DIV>
<DIZ><FONT face=3DGeorgia>Source: ScienceNews<BR><A=20 href=3-
D"http://www.sciencenews.org/articles/20070120/fob6.asp"-
>http://www= .sciencenews.org/articles/20070120/fob6.asp-
</A></FONT></DIV>
<DIZ><FONT face=3DGeorgia></FONT> </DIV>
<DIZ><FONT face=3DGeorgia>Posted by<BR>Robert Karl=20
Stonjek</FONT></DIV></DIV></BODY></HTML>
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quoted-printable
Going Under Down Under: Early people at fault in Australian
extinctions Sid Perkins
A lengthy, newly compiled fossil record of Australian
mammals bolsters = the notion that humanity's arrival on the
island continent led to the = extinction of many large
creatures there.=20
Archaeological evidence suggests that people arrived in
northern and = western Australia about 50,000 years ago (SN:
3/15/03, p. 173: Available = to subscribers at =
http://www.sciencenews.org/articles/20030315/note10.asp). By
5,000 years = later, about 90 percent of the continent's
mammals larger than a house = cat had gone extinct, says Gavin
J. Prideaux, a paleontologist at the = Western Australian
Museum in Perth. Casualties of that era include = several
species of kangaroos and wombats as well as marsupials that =
filled the ecological niches elsewhere populated by lions,
hyenas, = hippos, and tapirs.=20
By unearthing and cataloging specimens from a group of
fossil-rich caves = about 300 kilometers southeast of
Adelaide, Prideaux and his colleagues = assembled a nearly
complete record of the past 500,000 years. Most of = the 62
species of nonflying mammals on the list fell into the caverns
= via sinkholes, but some remains were brought in by owls that
roosted = there.=20
Scientists had compiled a long-term climate record for
southeastern = Australia by analyzing the caves' stalactites.
Those structures formed = and grew when rainfall was plentiful
but not during dry spells.=20
During most of the past 500,000 years, the number and
diversity of = mammal fossils found in the Australian caves
decreased only during = intervals when the local climate was
dry. When moisture returned, so did = the animals. The only
exception is the die-off of mammals between 50,000 = and
45,000 years ago, the team reports in the January Geology.=20
Those extinctions occurred at least 25,000 years before the
most recent = ice age began. "The climate was stable then, and
mammals really = shouldn't have been going extinct," says
coauthor Richard G. Roberts, a = geochemist at the University
of Wollongong in Australia. "The only thing = that's new
during that period is people," he adds.=20
Scientists are debating how people might have caused the
extinctions. = Some researchers argue that the new inhabitants
drastically altered = Australian ecosystems by burning the
landscape (SN: 7/23/05, p. 61: = Available to subscribers at =
http://www.sciencenews.org/articles/20050723/note11.asp).
However, large = species may have died off gradually when
people preyed on the mammals' = offspring faster than the
animals reproduced, says Roberts.=20
The fossil record compiled by Prideaux and his colleagues
shows that = "the mammal fauna was resilient through time,
despite climate = fluctuations," says David W. Steadman, a
paleontologist at the = University of Florida in Gainesville.
Changes in mammal populations = during times of climate change
"were nothing like those that occurred = after people showed
up," he notes.=20
"To think climate caused these extinctions is [now]
untenable," comments = Gifford H. Miller, a geologist at the
University of Colorado at Boulder. =
--------------------------------------------------------------
------------=
-------
If you have a comment on this article that you would
like = considered for publication in Science News, send
it to = editors@sciencenews.org. Please include your
name and location. =20
Source: ScienceNews
http://www.sciencenews.org/articles/20070120/fob6.asp
Posted by Robert Karl Stonjek
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD> <META http-equiv=3DContent-Type
content=3D"text/html; = charset=3Diso-8859-1"> <META
content=3D"MSHTML 6.00.3790.1218" name=3DGENERATOR>
<STYLE></STYLE> </HEAD> <BODY>
<DIV>
<DIW>
<DIW1>Going Under Down Under: Early people at fault in
Australian = extinctions</H3>
<DIX><STRONG>Sid Perkins</STRONG></P>
<DIY>A lengthy, newly compiled fossil record of Australian
mammals = bolsters the=20 notion that humanity's arrival
on the island continent led to the = extinction of=20
many large creatures there.=20
<DIZ>Archaeological evidence suggests that people arrived in
northern and = western=20 Australia about 50,000 years
ago (SN: 3/15/03, p. 173: Available to = subscribers=20
at <A=20 href=3D"http://www.sciencenews.org/articles/200-
30315/note10.asp">http://w=
ww.sciencenews.org/articles/20030315/note10.asp</A>).=20
By 5,000 years later, about 90 percent of the continent's
mammals larger = than a=20 house cat had gone extinct,
says Gavin J. Prideaux, a paleontologist at = the=20
Western Australian Museum in Perth. Casualties of that
era include = several=20 species of kangaroos and wombats
as well as marsupials that filled the=20 ecological
niches elsewhere populated by lions, hyenas, hippos, and
= tapirs.=20
<DIZ>By unearthing and cataloging specimens from a group of
fossil-rich = caves=20 about 300 kilometers southeast of
Adelaide, Prideaux and his colleagues=20 assembled a
nearly complete record of the past 500,000 years. Most of
= the 62=20 species of nonflying mammals on the list fell
into the caverns via = sinkholes,=20 but some remains
were brought in by owls that roosted there.=20
<DIZ>Scientists had compiled a long-term climate record for
southeastern = Australia=20 by analyzing the caves'
stalactites. Those structures formed and grew = when=20
rainfall was plentiful but not during dry spells.=20
<DIZ>During most of the past 500,000 years, the number and
diversity of = mammal=20 fossils found in the Australian
caves decreased only during intervals = when the=20 local
climate was dry. When moisture returned, so did the
animals. The = only=20 exception is the die-off of
mammals between 50,000 and 45,000 years ago, = the=20
team reports in the January <I>Geology</I>.=20
<DIZ>Those extinctions occurred at least 25,000 years before
the most = recent ice=20 age began. "The climate was
stable then, and mammals really shouldn't = have been=20
going extinct," says coauthor Richard G. Roberts, a
geochemist at the = University=20 of Wollongong in
Australia. "The only thing that's new during that =
period is=20 people," he adds.=20
<DIZ>Scientists are debating how people might have caused the
extinctions. = Some=20 researchers argue that the new
inhabitants drastically altered = Australian=20
ecosystems by burning the landscape (SN: 7/23/05, p. 61:
Available to=20 subscribers at <A=20 href=3D"http://www.-
sciencenews.org/articles/20050723/note11.asp">http://w=
ww.sciencenews.org/articles/20050723/note11.asp</A>).=20
However, large species may have died off gradually when
people preyed on = the=20 mammals' offspring faster than
the animals reproduced, says Roberts.=20
<DIZ>The fossil record compiled by Prideaux and his colleagues
shows that = "the=20 mammal fauna was resilient through
time, despite climate fluctuations," = says=20 David W.
Steadman, a paleontologist at the University of Florida
in = Gainesville.=20 Changes in mammal populations during
times of climate change "were = nothing like=20 those
that occurred after people showed up," he notes.=20
<DIZ>"To think climate caused these extinctions is [now]
untenable," = comments=20 Gifford H. Miller, a geologist
at the University of Colorado at Boulder. =
<DIZ></P> <HR width=3D"75%">
<DIV align=3Dcenter> <TABLE cellSpacing=3D0 cellPadding=3D0
width=3D430 border=3D0> <TBODY> <TR> <TD><FONT face=3DArial
size=3D2>If you have a comment on this = article that you=20
would like considered for publication in <I>Science News</I>,
send = it to=20 <A = href=3D"mailto:editors@sciencenews.org">-
editors@sciencenews.org</A>.=20 Please include your name and
location.</FONT>=20 </TD></TR></TBODY></TABLE></DIV></DIV>
<DIZ><FONT face=3DGeorgia>Source: ScienceNews<BR><A=20 href=3-
D"http://www.sciencenews.org/articles/20070120/fob6.asp"-
>http://www= .sciencenews.org/articles/20070120/fob6.asp-
</A></FONT></DIV>
<DIZ><FONT face=3DGeorgia></FONT> </DIV>
<DIZ><FONT face=3DGeorgia>Posted by<BR>Robert Karl=20
Stonjek</FONT></DIV></DIV></BODY></HTML>
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