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Just as new species are constantly evolving, old ones are going extinct. Such background level extinctions are the consequence of natural selection, when species can no longer cope due to changes in their ecosystems to which they can’t adequately adapt. One of those changes is the evolution of new species. The march of evolution is not, however, some sort of progress, in which species are becoming better and better. This is teleological thinking, like the Great Chain of Being (), and has no scientific value.
There’s also no evidence for built-in senescence or obsolescence of species, which makes sense: there’s no way to select for such a trait, just as there’s no way to select for a trait ahead of time that would be a useful response to a future, novel challenge. We can also rule out the idea that species can acquire traits through the life experience of individuals. There’s no mechanism whereby your offspring can be made stronger through inheritance of a strength you’ve acquired by pumping iron, because there’s no way to program your genes to specify the acquired property.
It is possible to make an ecosystem more vulnerable to collapse, by lessening its biological diversity. A healthy ecosystem rarely depends on any particular species for survival, because variations in the environment select in favor of naturally occurring diversification of the gene pool within and across species. An ecosystem is more fragile (subject to partial or total collapse through the extinction of many species) when this diversity is weakened, however. Within a species, decreased diversity limits the environmental challenges to which it can adapt. Across species, if all but one species serving a key role disappear (e.g., if there’s only one kind of tree left in a forest), it becomes a keystone species, and without it the ecosystem collapses.
Widespread geographical distributions protect species. If a local community is demolished by the death of a reef or by a tsunami, the species that are widespread enough will survive. Habitat shrinkage to a small region of the globe can bring such species to the brink of extinction. What’s different about a mass extinction?
It has to be global, or nearly so, so that essentially every member of a species driven to extinction fails to propagate, wherever it may be.
It has to be broad-spectrum, affecting enough species that it causes global ecological collapse.
It has to be really, really bad luck, in that it isn’t a routine challenge to species. In other words, it has to be outside the realm of natural selection. We can’t blame the victims’ genes for their fate.
It usually has to be triggered, so that once begun it’s inexorable. There are two kinds of triggered processes: (1) those in which the system is semi-stable, like a house of cards (think mortally weakened ecosystem), or (2) those in which positive feedback (destabilizing) mechanisms overwhelm negative feedback (stabilizing) ones. In either case, the environmental challenge has to be big enough, widespread enough and long-lasting enough to do the job.
What kinds of challenges meet these requirements? There are two that have been documented, both of them more than once: global cooling and global decrease in oxygen.
Cooling has been brought about by supercontinent formation or drift of a continent over one of Earth’s poles, and subsequent widespread glaciation; or increased albedo due to volcanism or meteorite impact. Note that glaciation also increases albedo, a positive feedback effect. Glaciation also causes a fall in sea level (oceanic regression)
Decreased oxygen has been associated with oceanic regression, in which sea levels dropped substantially. One proposed link is the exposure of large areas of continental shelf. When the sea organisms dwelling in these areas are exposed to air they die, and their subsequent decay consumes atmospheric oxygen. Continental and oceanic organisms most dependent on oxygen die next as a result, initiating another positive-feedback cycle which remorselessly continues until the least oxygen-dependent or most-protected species are the only ones left.
The present mass extinction doesn’t quite fit these descriptions. How’s it different and what’s driving it? Stay tuned.
I recommend Niles Eldridge, The Miner’s Canary (1991) for further reading.
Links:
Mexico Hot over Proposed US Wall, http://www.truthout.org/docs_2006/010406H.shtm
l Oil Boom a Bust for Villagers, http://www.truthout.org/issues_06/010406EA.shtml
Trade in wild caviar banned, http://www.newscientist.com/article.ns?id=dn8528
Warming shifted currents, http://www.nature.com/news/2006/060102/full/060102-5.html
Governor seeks 90% mercury reduction, http://www.chicagotribune.com/news/nationworld/chi-0601050073jan05,1,762...
Car emission suit, http://pressherald.mainetoday.com/news/state/060105lawsuit.shtml
N Atlantic fish on brink of extinction, http://news.bbc.co.uk/1/hi/sci/tech/4581428.stm
Evacuate 97K in China, http://www.sinodaily.com/2006/060105082049.pkzwfdxd.html
Climate change refugees, http://www.spacedaily.com/2006/060105063619.6g3qonet.html
Earth-Friendly Materials Go Mainstream, http://www.nytimes.com/2006/01/05/garden/05green.html?ex=1294117200&en=f...
The Tofte Cabin, http://www.tofteproject.org/
Brave Neuro World, http://www.truthout.org/issues_06/010506HA.shtml
Women's Campaign against Alito, http://www.truthout.org/issues_06/010506WA.shtml
Vatican's Abortion Treaty, http://www.truthout.org/issues_06/010506WB.shtml
Robertson: God smote Sharon, http://www.cnn.com/2006/US/01/05/robertson.sharon/index.html
Renewable Energy Firms Cash In, http://www.terradaily.com/news/US_Renewable_Energy_Firms_Cash_In.html
Is is safe to eat salmon? http://www.thestar.com/NASApp/cs/ContentServer?pagename=thestar/Layout/
Article_Type1&c=Article&cid=1136501415863&call_pageid=968332188774&col=968350116467
The geopolitics of natural gas, http://www.thenation.com/doc/20060123/klare
Population Threat to Climate Change Fight, http://www.commondreams.org/headlines06/0106-01.htm
WI abortion veto, http://www.cnn.com/2006/POLITICS/01/07/wisconsin.abortion.ap/index.html
Coal is king again, http://www.chicagotribune.com/business/chi-0601080253jan08,1,264124.stor...
Tiny Crystals Promise Big Benefits for Solar Technologies, http://www.spacedaily.com/news/Tiny_Crystals_Promise_Big_Benefits_For_So...
Ministers warned of huge rise in nuke waste, http://www.guardian.co.uk/waste/story/0,12188,1682088,00.html
Dawkins: Religion equals 'child abuse', http://wnd.com/news/article.asp?ARTICLE_ID=48252
Get Pombo , http://www.grist.org/news/muck/2006/01/06/pombo/index.html?source=daily
Whales in deep trouble, http://www.commondreams.org/headlines06/0109-02.htm
Rewriting Glacial History In Pacific NW, http://www.terradaily.com/news/Rewriting_Glacial_History_In_Pacific_Nort...
Nobel Laureate Blames E Africa Drought On Deforestation, http://www.terradaily.com/news/Nobel_Laureate_Blames_EAfrica_Drought_On_...
Australia Warns No 'Silver Bullet' At Climate Meet, http://www.terradaily.com/news/Australia_Warns_No_Silver_Bullet_At_Clima...
Iran Resumes Its Nuclear Project, http://www.truthout.org/docs_2006/010906G.shtml
A Killer Takes Wing, http://www.latimes.com/news/science/la-sci-birdflu10jan10,1,5031464.stor...
Bird flu spreads in Turkey, http://news.independent.co.uk/europe/article337584.ece
Effect of warming to hit poor hardest, http://www.freenewmexican.com/news/37513.html
Fines in mining deaths cut back, http://usatoday.com/news/nation/2006-01-09-mine-fines_x.htm
Ruling reinstates species protections, http://seattlepi.nwsource.com/local/255094_forest10.html
U.S. Research Budget Worries Scientists, http://www.townhall.com/news/ap/online/science/D8ES3RLG4.html
Character Training Institute Kingdom of God, http://www.truthout.org/docs_2006/011006H.shtml
Govts Against US Border Fence, http://www.commondreams.org/headlines06/0110-08.htm
China's Race for Energy Resources Only Just Heating Up, http://www.terradaily.com/news/Chinas_Race_For_Energy_Resources_Only_Jus...
Researchers Confirm Role of Massive Flood in Climate Change, http://www.terradaily.com/news/The_Role_Of_Massive_Floods_In_Climate_Cha...
Dance of The Atmosphere and Oceans, http://www.terradaily.com/news/
Intricate_Dance_Of_The_Atmosphere_And_Oceans.html
US Seeks Dutch Dams Expertise after Katrina, http://www.terradaily.com/news/US_Seeks_Dutch_Dams_Expertise_After_Katri...
200+ Dead As S Asia Gripped By Icy Weather, http://www.terradaily.com/news/200_Plus_Dead_As_S_Asia_Gripped_By_Icy_We...
Rise and Fall of True Believers, http://www.truthout.org/docs_2006/011106D.shtml
Pat Robertson and Theodicy ad Absurdum, http://www.truthdig.com/report/item/20060110_pat_robertson/
Shrinking Arctic ice trouble for world, http://www.realcities.com/mld/krwashington/13593302.htm
Industry deal on climate, http://www.theaustralian.news.com.au/common/story_page/0,5744,17787734%2...
Climate Fears, Water Shortages Haunt Europe, http://www.planetark.org/dailynewsstory.cfm/newsid/34427/story.htm
Stricter Nanotechnology Laws Are Urged, http://www.washingtonpost.com/wp-dyn/content/article/2006/01/10/AR200601...
Having trouble breathing? http://home.hamptonroads.com/stories/story.cfm?story=97924&ran=246313&tr...
MetroWest Fines To Cut Car Use, http://www.washingtonpost.com/wp-dyn/content/article/2006/01/10/AR200601...
Science takes hard look inward, http://www.usatoday.com/tech/science/ethics/2006-01-10-journal-fraud_x.htm
Whole Foods wind power, http://www.usatoday.com/money/industries/food/2006-01-09-whole-foods-usa...
Salvage Logging Hurts Forests, http://www.christiansciencemonitor.com/2006/0110/p02s02-sten.html
Major Polluters Launch Controversial Global Warming Talks, http://www.commondreams.org/headlines06/0111-03.htm
Could Forests Worsen Global Warming? http://www.terradaily.com/news/Could_Forests_Worsen_Global_Warming.html
Deep-Rooted Plants Impact On Climate, http://www.terradaily.com/news/Deep_Rooted_Plants_Have_Great_Impact_On_C...
Extinctions Linked To Climate Change, http://www.terradaily.com/news/Extinctions_Linked_To_Climate_Change.html
"Doomsday Vault" To House World's Seeds, http://www.terradaily.com/news/Doomsday_Vault_To_House_Worlds_Seeds.html
1st suit in CA against 'intelligent design', http://www.truthout.org/docs_2006/011106G.shtml
Asia’s Big Freeze, http://www.truthout.org/issues_06/011106EB.shtml
New Bird Flu Findings, http://www.truthout.org/issues_06/011106HA.shtml
Pollution control immunity proposed, http://www.baltimoresun.com/news/local/bal-te.md.mde12jan12,1,7412469.st...
Bottled water given to residents also tainted, http://www.columbusdispatch.com/news-story.php?story=dispatch/2006/01/12...
50,000 new fossil fuel wells in West, http://www.denverpost.com/nationworld/ci_3394014
Climate culprit for frog deaths, http://news.bbc.co.uk/1/hi/world/asia-pacific/4602116.stm
Greenhouse battle handed to industry, http://www.smh.com.au/news/national/greenhouse-battle-handed-to-industry...
Growth for Biotech Crops, http://www.washingtonpost.com/wp-dyn/content/article/2006/01/11/AR200601...
Japan's new energy strategy, http://www.atimes.com/atimes/Japan/HA13Dh01.html
CA to invest $Bs in solar power, http://www.mercurynews.com/mld/mercurynews/news/local/13607694.htm
Living plants emit methane, http://www.newscientist.com/channel/earth/mg18925343.900
Algae clean smokestack emissions, http://www.christiansciencemonitor.com/2006/0111/p01s03-sten.html
Lax Oversight of Gene-Altered Crops, http://www.organicconsumers.org/ge/oversight010406.cfm
US Lifts Longtime Drilling Ban in Alaska, http://www.truthout.org/docs_2006/011206B.shtml
China-India Oil Alliance, http://www.truthout.org/docs_2006/011306L.shtml
Regulators OK CA Solar Proposal, http://www.truthout.org/issues_06/011306EB.shtml
Some get global warming, some don't, http://www.truthout.org/issues_06/011306EC.shtml
Kenya's drought, 2.5 M at risk of famine, http://www.truthout.org/issues_06/011306HA.shtml
Bird Flu Mutation Raises Threat to Humans, http://www.truthout.org/issues_06/011306HB.shtml
Abortion Politics, http://www.truthout.org/issues_06/011306WA.shtml
The clock is ticking.
---
Paul Brown is a professor of Physiology at West Virginia University. He can be contacted at pbrown@clockticking.com. Previous columns and other resources can be accessed on the Web at http://clockticking.com. For a free weekly email subscription, send an email (no message necessary) to subscribe@clockticking.com. To unsubscribe, send an email (no message necessary) to unsubscribe@clockticking.com. Copyright 2005 by Paul B. Brown
There’s also no evidence for built-in senescence or obsolescence of species, which makes sense: there’s no way to select for such a trait, just as there’s no way to select for a trait ahead of time that would be a useful response to a future, novel challenge. We can also rule out the idea that species can acquire traits through the life experience of individuals. There’s no mechanism whereby your offspring can be made stronger through inheritance of a strength you’ve acquired by pumping iron, because there’s no way to program your genes to specify the acquired property.
It is possible to make an ecosystem more vulnerable to collapse, by lessening its biological diversity. A healthy ecosystem rarely depends on any particular species for survival, because variations in the environment select in favor of naturally occurring diversification of the gene pool within and across species. An ecosystem is more fragile (subject to partial or total collapse through the extinction of many species) when this diversity is weakened, however. Within a species, decreased diversity limits the environmental challenges to which it can adapt. Across species, if all but one species serving a key role disappear (e.g., if there’s only one kind of tree left in a forest), it becomes a keystone species, and without it the ecosystem collapses.
Widespread geographical distributions protect species. If a local community is demolished by the death of a reef or by a tsunami, the species that are widespread enough will survive. Habitat shrinkage to a small region of the globe can bring such species to the brink of extinction. What’s different about a mass extinction?
It has to be global, or nearly so, so that essentially every member of a species driven to extinction fails to propagate, wherever it may be.
It has to be broad-spectrum, affecting enough species that it causes global ecological collapse.
It has to be really, really bad luck, in that it isn’t a routine challenge to species. In other words, it has to be outside the realm of natural selection. We can’t blame the victims’ genes for their fate.
It usually has to be triggered, so that once begun it’s inexorable. There are two kinds of triggered processes: (1) those in which the system is semi-stable, like a house of cards (think mortally weakened ecosystem), or (2) those in which positive feedback (destabilizing) mechanisms overwhelm negative feedback (stabilizing) ones. In either case, the environmental challenge has to be big enough, widespread enough and long-lasting enough to do the job.
What kinds of challenges meet these requirements? There are two that have been documented, both of them more than once: global cooling and global decrease in oxygen.
Cooling has been brought about by supercontinent formation or drift of a continent over one of Earth’s poles, and subsequent widespread glaciation; or increased albedo due to volcanism or meteorite impact. Note that glaciation also increases albedo, a positive feedback effect. Glaciation also causes a fall in sea level (oceanic regression)
Decreased oxygen has been associated with oceanic regression, in which sea levels dropped substantially. One proposed link is the exposure of large areas of continental shelf. When the sea organisms dwelling in these areas are exposed to air they die, and their subsequent decay consumes atmospheric oxygen. Continental and oceanic organisms most dependent on oxygen die next as a result, initiating another positive-feedback cycle which remorselessly continues until the least oxygen-dependent or most-protected species are the only ones left.
The present mass extinction doesn’t quite fit these descriptions. How’s it different and what’s driving it? Stay tuned.
I recommend Niles Eldridge, The Miner’s Canary (1991) for further reading.
Links:
Mexico Hot over Proposed US Wall, http://www.truthout.org/docs_2006/010406H.shtm
l Oil Boom a Bust for Villagers, http://www.truthout.org/issues_06/010406EA.shtml
Trade in wild caviar banned, http://www.newscientist.com/article.ns?id=dn8528
Warming shifted currents, http://www.nature.com/news/2006/060102/full/060102-5.html
Governor seeks 90% mercury reduction, http://www.chicagotribune.com/news/nationworld/chi-0601050073jan05,1,762...
Car emission suit, http://pressherald.mainetoday.com/news/state/060105lawsuit.shtml
N Atlantic fish on brink of extinction, http://news.bbc.co.uk/1/hi/sci/tech/4581428.stm
Evacuate 97K in China, http://www.sinodaily.com/2006/060105082049.pkzwfdxd.html
Climate change refugees, http://www.spacedaily.com/2006/060105063619.6g3qonet.html
Earth-Friendly Materials Go Mainstream, http://www.nytimes.com/2006/01/05/garden/05green.html?ex=1294117200&en=f...
The Tofte Cabin, http://www.tofteproject.org/
Brave Neuro World, http://www.truthout.org/issues_06/010506HA.shtml
Women's Campaign against Alito, http://www.truthout.org/issues_06/010506WA.shtml
Vatican's Abortion Treaty, http://www.truthout.org/issues_06/010506WB.shtml
Robertson: God smote Sharon, http://www.cnn.com/2006/US/01/05/robertson.sharon/index.html
Renewable Energy Firms Cash In, http://www.terradaily.com/news/US_Renewable_Energy_Firms_Cash_In.html
Is is safe to eat salmon? http://www.thestar.com/NASApp/cs/ContentServer?pagename=thestar/Layout/
Article_Type1&c=Article&cid=1136501415863&call_pageid=968332188774&col=968350116467
The geopolitics of natural gas, http://www.thenation.com/doc/20060123/klare
Population Threat to Climate Change Fight, http://www.commondreams.org/headlines06/0106-01.htm
WI abortion veto, http://www.cnn.com/2006/POLITICS/01/07/wisconsin.abortion.ap/index.html
Coal is king again, http://www.chicagotribune.com/business/chi-0601080253jan08,1,264124.stor...
Tiny Crystals Promise Big Benefits for Solar Technologies, http://www.spacedaily.com/news/Tiny_Crystals_Promise_Big_Benefits_For_So...
Ministers warned of huge rise in nuke waste, http://www.guardian.co.uk/waste/story/0,12188,1682088,00.html
Dawkins: Religion equals 'child abuse', http://wnd.com/news/article.asp?ARTICLE_ID=48252
Get Pombo , http://www.grist.org/news/muck/2006/01/06/pombo/index.html?source=daily
Whales in deep trouble, http://www.commondreams.org/headlines06/0109-02.htm
Rewriting Glacial History In Pacific NW, http://www.terradaily.com/news/Rewriting_Glacial_History_In_Pacific_Nort...
Nobel Laureate Blames E Africa Drought On Deforestation, http://www.terradaily.com/news/Nobel_Laureate_Blames_EAfrica_Drought_On_...
Australia Warns No 'Silver Bullet' At Climate Meet, http://www.terradaily.com/news/Australia_Warns_No_Silver_Bullet_At_Clima...
Iran Resumes Its Nuclear Project, http://www.truthout.org/docs_2006/010906G.shtml
A Killer Takes Wing, http://www.latimes.com/news/science/la-sci-birdflu10jan10,1,5031464.stor...
Bird flu spreads in Turkey, http://news.independent.co.uk/europe/article337584.ece
Effect of warming to hit poor hardest, http://www.freenewmexican.com/news/37513.html
Fines in mining deaths cut back, http://usatoday.com/news/nation/2006-01-09-mine-fines_x.htm
Ruling reinstates species protections, http://seattlepi.nwsource.com/local/255094_forest10.html
U.S. Research Budget Worries Scientists, http://www.townhall.com/news/ap/online/science/D8ES3RLG4.html
Character Training Institute Kingdom of God, http://www.truthout.org/docs_2006/011006H.shtml
Govts Against US Border Fence, http://www.commondreams.org/headlines06/0110-08.htm
China's Race for Energy Resources Only Just Heating Up, http://www.terradaily.com/news/Chinas_Race_For_Energy_Resources_Only_Jus...
Researchers Confirm Role of Massive Flood in Climate Change, http://www.terradaily.com/news/The_Role_Of_Massive_Floods_In_Climate_Cha...
Dance of The Atmosphere and Oceans, http://www.terradaily.com/news/
Intricate_Dance_Of_The_Atmosphere_And_Oceans.html
US Seeks Dutch Dams Expertise after Katrina, http://www.terradaily.com/news/US_Seeks_Dutch_Dams_Expertise_After_Katri...
200+ Dead As S Asia Gripped By Icy Weather, http://www.terradaily.com/news/200_Plus_Dead_As_S_Asia_Gripped_By_Icy_We...
Rise and Fall of True Believers, http://www.truthout.org/docs_2006/011106D.shtml
Pat Robertson and Theodicy ad Absurdum, http://www.truthdig.com/report/item/20060110_pat_robertson/
Shrinking Arctic ice trouble for world, http://www.realcities.com/mld/krwashington/13593302.htm
Industry deal on climate, http://www.theaustralian.news.com.au/common/story_page/0,5744,17787734%2...
Climate Fears, Water Shortages Haunt Europe, http://www.planetark.org/dailynewsstory.cfm/newsid/34427/story.htm
Stricter Nanotechnology Laws Are Urged, http://www.washingtonpost.com/wp-dyn/content/article/2006/01/10/AR200601...
Having trouble breathing? http://home.hamptonroads.com/stories/story.cfm?story=97924&ran=246313&tr...
MetroWest Fines To Cut Car Use, http://www.washingtonpost.com/wp-dyn/content/article/2006/01/10/AR200601...
Science takes hard look inward, http://www.usatoday.com/tech/science/ethics/2006-01-10-journal-fraud_x.htm
Whole Foods wind power, http://www.usatoday.com/money/industries/food/2006-01-09-whole-foods-usa...
Salvage Logging Hurts Forests, http://www.christiansciencemonitor.com/2006/0110/p02s02-sten.html
Major Polluters Launch Controversial Global Warming Talks, http://www.commondreams.org/headlines06/0111-03.htm
Could Forests Worsen Global Warming? http://www.terradaily.com/news/Could_Forests_Worsen_Global_Warming.html
Deep-Rooted Plants Impact On Climate, http://www.terradaily.com/news/Deep_Rooted_Plants_Have_Great_Impact_On_C...
Extinctions Linked To Climate Change, http://www.terradaily.com/news/Extinctions_Linked_To_Climate_Change.html
"Doomsday Vault" To House World's Seeds, http://www.terradaily.com/news/Doomsday_Vault_To_House_Worlds_Seeds.html
1st suit in CA against 'intelligent design', http://www.truthout.org/docs_2006/011106G.shtml
Asia’s Big Freeze, http://www.truthout.org/issues_06/011106EB.shtml
New Bird Flu Findings, http://www.truthout.org/issues_06/011106HA.shtml
Pollution control immunity proposed, http://www.baltimoresun.com/news/local/bal-te.md.mde12jan12,1,7412469.st...
Bottled water given to residents also tainted, http://www.columbusdispatch.com/news-story.php?story=dispatch/2006/01/12...
50,000 new fossil fuel wells in West, http://www.denverpost.com/nationworld/ci_3394014
Climate culprit for frog deaths, http://news.bbc.co.uk/1/hi/world/asia-pacific/4602116.stm
Greenhouse battle handed to industry, http://www.smh.com.au/news/national/greenhouse-battle-handed-to-industry...
Growth for Biotech Crops, http://www.washingtonpost.com/wp-dyn/content/article/2006/01/11/AR200601...
Japan's new energy strategy, http://www.atimes.com/atimes/Japan/HA13Dh01.html
CA to invest $Bs in solar power, http://www.mercurynews.com/mld/mercurynews/news/local/13607694.htm
Living plants emit methane, http://www.newscientist.com/channel/earth/mg18925343.900
Algae clean smokestack emissions, http://www.christiansciencemonitor.com/2006/0111/p01s03-sten.html
Lax Oversight of Gene-Altered Crops, http://www.organicconsumers.org/ge/oversight010406.cfm
US Lifts Longtime Drilling Ban in Alaska, http://www.truthout.org/docs_2006/011206B.shtml
China-India Oil Alliance, http://www.truthout.org/docs_2006/011306L.shtml
Regulators OK CA Solar Proposal, http://www.truthout.org/issues_06/011306EB.shtml
Some get global warming, some don't, http://www.truthout.org/issues_06/011306EC.shtml
Kenya's drought, 2.5 M at risk of famine, http://www.truthout.org/issues_06/011306HA.shtml
Bird Flu Mutation Raises Threat to Humans, http://www.truthout.org/issues_06/011306HB.shtml
Abortion Politics, http://www.truthout.org/issues_06/011306WA.shtml
The clock is ticking.
---
Paul Brown is a professor of Physiology at West Virginia University. He can be contacted at pbrown@clockticking.com. Previous columns and other resources can be accessed on the Web at http://clockticking.com. For a free weekly email subscription, send an email (no message necessary) to subscribe@clockticking.com. To unsubscribe, send an email (no message necessary) to unsubscribe@clockticking.com. Copyright 2005 by Paul B. Brown