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   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Early crop plants were more easily 'tamed'    
      
     Date:   
         April 10, 2023   
     Source:   
         Washington University in St. Louis   
     Summary:   
         Borrowing a page from what we know about animal behavior,   
         archaeologists say that we should reassess our understanding of   
         the process of plant domestication.   
      
      
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   FULL STORY   
   ==========================================================================   
   The story of how ancient wolves came to claim a place near the campfire   
   as humanity's best friend is a familiar tale (even if scientists are   
   still working out some of the specifics). In order to be domesticated,   
   a wild animal must be tamable -- capable of living in close proximity   
   to people without exhibiting dangerous aggression or debilitating   
   fear. Taming was the necessary first step in animal domestication,   
   and it is widely known that some animals are easier to tame than others.   
      
      
   ==========================================================================   
   But did humans also favor certain wild plants for domestication because   
   they were more easily "tamed"? Research from Washington University in   
   St. Louis calls for a reappraisal of the process of plant domestication,   
   based on almost a decade of observations and experiments. The behavior   
   of erect knotweed, a buckwheat relative, has WashU paleoethnobotanists   
   completely reassessing our understanding of plant domestication.   
      
   "We have no equivalent term for tameness in plants," said Natalie   
   Mueller, assistant professor of archaeology in Arts & Sciences at   
   Washington University.   
      
   "But plants are capable of responding to people. They have a developmental   
   capacity to be tamed."  Her work with early indigenous North American   
   crops shows that some wild plants respond quickly to clearing,   
   fertilizing, weeding or thinning. Plants that respond in ways that make   
   cultivation easier or more productive could be considered more easily   
   tamed than those that cannot.   
      
   "If plants responded rapidly in ways that were beneficial to early   
   cultivators -- for example by producing higher yields, larger seeds,   
   seeds that were easier to sprout, or a second crop in a single growing   
   season -- this would have encouraged humans to continue investing in   
   the co-evolutionary relationship," she said.   
      
   This capacity to express different traits and characteristics in response   
   to the environment is called plasticity, and not all species are equally   
   plastic.   
      
   "Some plants respond quickly and obviously to cultivation and care,"   
   Mueller said. "I think ancient people would have noticed that they could   
   double their yields just by thinning out dense stands of plants. This   
   is one of the simplest and most common gardening techniques, but it   
   has many important effects on the development of plants."  What would   
   an early farmer do?  Mueller's study, published April 7 in PLOS ONE,   
   focuses on work with a plant called erect knotweed, a member of the   
   buckwheat family that was domesticated by indigenous farmers in eastern   
   North America. The domesticated sub-species is now extinct; humans don't   
   eat it anymore. But Mueller and others have previously uncovered caches   
   of seeds stored in caves, charred plant remnants in ancient hearths,   
   and even the seeds of erect knotweed in human feces, clear evidence that   
   this species was once consumed as a staple food.   
      
   Mueller, who studies lost crops, has spent years growing erect knotweed   
   and other crop progenitors in experimental gardens, including at   
   Washington University's environmental field station, Tyson Research   
   Center. She hasn't always been successful with growing the plants she   
   collects in the wild. In that way, Mueller can relate to the early farmers   
   who similarly experimented with plants to discover their potential.   
      
   Her efforts have often been stymied by seed dormancy, a common feature   
   among wild plants.   
      
   Unlike seeds you buy at the garden store, the seeds of most wild plants   
   will not germinate if you simply sprinkle some water on them. Their   
   requirements for germination are diverse and shaped by their evolutionary   
   history. For example, if a plant has evolved in a place with a winter,   
   like the Midwest, its seeds may not germinate unless they experience a   
   long cold period. This prevents them from germinating too soon in the   
   wild -- they are waiting for spring.   
      
   Domesticated plants have lost their diverse germination requirements.   
      
   The loss of germination inhibitors has presented a paradox to theorists   
   of domestication. Many of the selective pressures that could have favored   
   the evolution of this trait derive from planting seeds. But why would   
   ancient people have started planting seeds if none of them germinated?   
   With erect knotweed, Mueller experienced a breakthrough of sorts. Based on   
   four seasons of observations, Mueller determined that growing wild plants   
   in the low-density conditions typical of a cultivated garden (i.e. spaced   
   out and weeded) triggers plants to produce seeds that germinate more   
   easily. This makes the harvests easier to plant successfully the next   
   time around, eliminating a key barrier to further selection.   
      
   "Our results show that erect knotweed grown in low-density agroecosystems   
   spontaneously 'act domesticated' in a single growing season, before any   
   selection has occurred," Mueller said.   
      
   Think of it as the plant equivalent to that first wolf who, though still   
   a wild animal, sat down with its human friend around the fire. This is   
   a behavioral shift, rather than an evolutionary one, but it allows new   
   evolutionary pathways to open up.   
      
   A role for plant behavior Mueller believes there is a bias in   
   domestication studies toward viewing this changeability, or plasticity,   
   as noise that is getting in the way of attempts to explain evolutionary   
   change. Instead, this paper argues that we need to understand the   
   development and behavior of wild crop relatives in order to explain the   
   evolutionary process of domestication.   
      
   "Because we lack the practical experience with crop progenitors that   
   ancient people had, these effects of the environment on plant development   
   have gone mostly unnoticed and understudied," Mueller said.   
      
   Her findings could have applications for developing new food crops:   
   there is no reason why we have to be limited to the plants that our   
   ancestors domesticated thousands of years ago.   
      
   Some researchers have been calling for de novo domestication --   
   selecting wild plants with desirable characteristics and intentionally   
   domesticating them. It may make sense to start looking to wild plants   
   that are easily tamed as potential crops that could be developed for   
   the future, Mueller said.   
      
   This paper also contributes to a growing awareness that plants are   
   responsive and communicative beings. Though this idea is cutting-edge and   
   hotly debated in biology and ecology, it is widespread in indigenous North   
   American philosophies and probably would have been held by the people   
   who domesticated erect knotweed and other plants thousands of years ago.   
      
   Recent research has shown how plants warn relatives about herbivores   
   using chemical signaling, share resources through mycorrhizal networks   
   and even emit noises when they are injured or stressed.   
      
   "You can't explain plant domestication if you only consider the behaviors   
   of humans, because domestication is the result of reciprocal relationships   
   between multiple species that are all capable of responding to each   
   other," Mueller said.   
      
       * RELATED_TOPICS   
             o Plants_&_Animals   
                   # Endangered_Plants # Seeds # Botany   
             o Earth_&_Climate   
                   # Grassland # Rainforests # Ecology   
             o Fossils_&_Ruins   
                   # Human_Evolution # Evolution # Early_Humans   
       * RELATED_TERMS   
             o Corn o Archaeological_field_survey o Seed_predation o   
             Game_theory o Instinct o Mirror_neuron o Domestication o   
             Plant_breeding   
      
   ==========================================================================   
   Story Source: Materials provided by   
   Washington_University_in_St._Louis. Original written by Talia   
   Ogliore. Note: Content may be edited for style and length.   
      
      
   ==========================================================================   
   Journal Reference:   
      1. Natalie G. Mueller, Elizabeth T. Horton, Megan E. Belcher,   
      Logan Kistler.   
      
         The taming of the weed: Developmental plasticity facilitated plant   
         domestication. PLOS ONE, 2023; 18 (4): e0284136 DOI: 10.1371/   
         journal.pone.0284136   
   ==========================================================================   
      
   Link to news story:   
   https://www.sciencedaily.com/releases/2023/04/230410132158.htm   
      
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